Determinants of Pneumococcal Vaccination Decision‐Making Among High‑Risk Adults: A Qualitative Study Guided by the Theoretical Domains Framework

ABSTRACT

Background and Aims

Pneumococcal disease (PD) poses a substantial burden among older adults and individuals with chronic conditions, yet pneumococcal vaccination uptake remains suboptimal in Hong Kong. Understanding the psychological, social, and contextual determinants of pneumococcal vaccination decision‑making is essential for strengthening adult vaccination strategies.

Methods

A qualitative study was conducted among 24 adults from pneumococcal vaccination target groups. Semi‑structured interviews explored perceptions, motivations, and barriers related to PD and pneumococcal vaccination. Data were analysed using thematic analysis informed by the Theoretical Domains Framework (TDF). The TDF synthesizes constructs from behaviour change theories into 14 domains, enabling systematic examination of psychological, social, and contextual determinants of health behaviours.

Results

Over half of participants (13/24) expressed willingness to receive pneumococcal vaccination, though decisions were shaped by complex multi‑level influences. Trust in healthcare professionals and confidence in government recommendations, reflecting Social influences, emerged as commonly reported facilitators of vaccination. Financial support, such as subsidies or free vaccination, served as an important Reinforcement mechanism. The predominant barriers were limited understanding of pneumococcal vaccination and the vaccination programme (Knowledge), strong reliance on personal judgement in vaccination decision‐making (Social influences), and limited knowledge of PD (Knowledge). Participants also reported concerns about potential adverse effects (Beliefs about consequences), low perceived urgency (Intentions), and practical constraints, including limited accessibility of vaccination sites and appointment difficulties (Environmental context and resources), which were reported as additional barriers to vaccination.

Conclusions

Pneumococcal vaccination decision‐making among high‑risk adults was influenced by a combination of informational, psychological, social, and structural influences. Strengthening vaccine communication by healthcare professionals, improving awareness of and access to existing free or subsidised vaccination services, improving service accessibility, and delivering sustained public education may help address misconceptions, elevate perceived need, and improve pneumococcal vaccination coverage in Hong Kong.

Abbreviations

COVID‐19

Coronavirus disease 2019

HBM

Health Belief Model

IPD

Invasive pneumococcal disease

LRIs

Lower respiratory infections

NIPD

Non‐invasive pneumococcal disease

PCVs

Pneumococcal conjugate vaccines

PD

Pneumococcal disease

PPSV23

23‐valent pneumococcal polysaccharide vaccine

SBREC

Survey and Behavioural Research Ethics Committee

SRQR

Standards for Reporting Qualitative Research

TDF

Theoretical Domains Framework

VT‐CAP

Vaccine‐type community‐acquired pneumonia

VT‐IPD

Vaccine‐type invasive pneumococcal disease

1. Introduction

Pneumococcal disease (PD), caused by the bacterium Streptococcus pneumoniae, poses a substantial burden worldwide, especially among older adults, children, and adults with comorbidities [1, 2]. PD is typically classified into invasive pneumococcal disease (IPD) and non‐invasive pneumococcal disease (NIPD). Bacteraemic pneumonia, meningitis, and bacteraemia are common clinical presentations of IPD [3], which may lead to hospitalization and even death [4]. A study estimated that Streptococcus pneumoniae infection was a major cause of lower respiratory infections (LRIs), accounting for 97.9 million episodes and approximately 505,000 deaths globally in 2021 [1]. In Hong Kong, IPD has been a notifiable disease since 2015 [5, 6]. Based on the annual number of reported IPD cases from the Centre for Health Protection and Hong Kong population estimates, the estimated annual incidence between 2018 and 2022 ranged from 0.34 to 2.54 per 100,000 population, with a notable rebound in 2023 following the COVID‐19 pandemic [7]. A recent Hong Kong study analysing monthly trends of IPD and pneumococcal pneumonia between 2015 and 2023 found that IPD incidence rose in 2023, returning to pre‐pandemic levels and coinciding with relaxation of COVID‐19 mitigation measures [6]. Given the aging population, it is imperative to implement preventive measures and conduct ongoing surveillance of PD incidence in Hong Kong to alleviate the potential burden of PD.

Prevention is recognized as the backbone of reducing the burden of PD [8]. The introduction of pneumococcal vaccination has been instrumental in reducing the incidence of severe infections. Pneumococcal conjugate vaccines (PCVs) and the 23‐valent pneumococcal polysaccharide vaccine (PPSV23) are among the most widely used vaccines for adults [9]. A systematic review and meta‐analysis indicated that PPSV23 has been reported to provide 50%–54% effectiveness in preventing IPD and 4%–17% effectiveness against community‐acquired pneumonia among adults aged 50 and above [10]. Likewise, a systematic review and meta‐analysis reported an association between pneumococcal vaccination and 24% lower all‐cause mortality compared with no vaccination [11].

Since 2009, the Hong Kong Government's Pneumococcal Vaccination Programme has provided free or subsidised pneumococcal vaccination for eligible Hong Kong residents aged 65 years or above [12]. Older adults (aged 65 years or above) without high‐risk conditions are recommended to receive one dose of PPSV23, whereas those with high‐risk conditions are recommended to receive one dose of PCV15, followed by one dose of PPSV23 1 year later [13, 14]. Under the Vaccination Subsidy Scheme, government subsidies are provided for eligible vaccination through enrolled private doctors, while free vaccination is available for specified eligible groups through designated public clinics and residential care settings [13]. High‐risk conditions include a history of IPD, cerebrospinal fluid leakage, cochlear implant, chronic cardiovascular, lung, liver or kidney diseases, metabolic diseases, immunocompromised states, and chronic neurological conditions that compromise respiratory function or self‐care [13].

However, despite evidence supporting pneumococcal vaccination and recommendations from public health authorities, vaccination coverage remains unsatisfactory. In the U.S., pneumococcal vaccination coverage was reported at 69.0% among older adults aged 65 years and above [15]. In China, a study found that while 51.2% of residents expressed willingness to receive the pneumococcal vaccination, actual coverage was only 21.7% [16]. In Hong Kong, a recent study reported that 73.8% of participants expressed willingness to receive pneumococcal vaccination [17], yet available local evidence indicates that the actual pneumococcal vaccination uptake remains suboptimal, ranging from approximately 10% among community‐living older adults to around 20%–32% among eligible adults hospitalized for PD [18, 19]. Previous research has identified factors influencing vaccine hesitancy and uptake among pneumococcal vaccination recipients, including fear, lack of information, and limited resources [20]. These findings highlight the importance of understanding individuals' perspectives for the success of vaccination programmes.

In Hong Kong, despite the availability of a pneumococcal vaccination programme, a substantial gap remains between willingness to vaccinate and actual vaccine uptake. Understanding of PD and vaccination among target populations remains limited, which may reduce the effectiveness of vaccination programmes. Although previous studies in Hong Kong have identified factors associated with pneumococcal vaccination uptake, most have relied on quantitative approaches and provide limited insight into the underlying behavioural mechanisms driving vaccination decisions [17, 19]. Few studies have systematically explored how high‐risk adults perceive PD and vaccination through a comprehensive behavioural framework. The Theoretical Domains Framework (TDF) offers a useful approach for examining these determinants and informing intervention development. Therefore, this study aimed to explore the perceptions and attitudes of potential target populations toward pneumococcal vaccination using the TDF. By identifying key factors influencing vaccine decision‐making, this study sought to inform the development of effective strategies to support informed vaccination decisions and reduce the burden of PD in the community.

2. Methods

2.1. Study Design

In this qualitative study, individual semi‐structured interviews were carried out to capture participants' perceptions, attitudes, and experiences regarding pneumococcal vaccination in Hong Kong. The initial sample size was set at 20 participants based on evidence that data saturation could be achieved within 16 or fewer interviews in relatively homogeneous groups [21], as well as comparable sample sizes used in previous interview‐based qualitative studies [22, 23], with additional interviews planned if new themes continued to emerge. This study was reported in accordance with the Standards for Reporting Qualitative Research (SRQR) [24].

The interview guide was developed according to the TDF, which has been widely used to examine behaviour change and investigate implementation [25]. The TDF synthesises constructs from multiple behaviour change theories into theoretical domains, providing a theory‐informed approach to identifying determinants of behaviour [25]. It has been widely adopted in studies involving health service recipients to identify the mechanisms underlying health behaviour change [26, 27], and to inform the development of implementation interventions [28]. The TDF comprises 14 domains: Knowledge; Skills; Social/professional role and identity; Beliefs about capabilities; Optimism; Beliefs about consequences; Reinforcement; Intentions; Goals; Memory, attention and decision processes; Environmental context and resources; Social influences; Emotion; and Behavioural regulation, with domain definitions and constructs based on previous studies [25, 29]. These pre‐established domains and constructs were used to structure the interview guide and elicit participants' experiences, perceptions, and decision‐making processes.

2.2. Participants and Recruitment

Purposive sampling was employed to recruit four predefined participant groups to capture diverse perspectives across these groups, informed by the recommendations from the Centre for Health Protection in Hong Kong [30], including (1) individuals aged 18–49 years with at least one risk factor; (2) individuals aged 50–64 years with at least one risk factor; (3) individuals aged 65 years or above, with at least one risk factor; and (4) individuals aged 65 years or above, without risk factors. In this study, the risk factors for pneumococcal infection were defined as (1) alcohol abuse or smoking; (2) history of PD; (3) cerebrospinal fluid leakage; (4) cochlear implantation; (5) chronic cardiovascular disease (excluding isolated hypertension); (6) lung disease (chronic obstructive pulmonary disease, asthma); (7) chronic liver disease or kidney disease; (8) metabolic diseases (diabetes, obesity); (9) immunocompromised conditions (e.g., asplenia, HIV, cancer/frequent steroid therapy); and (10) chronic neurological diseases affecting breathing or self‐care. All participants were recruited from the Lek Yuen General Out‐patient Clinic in Hong Kong.

2.2.1. Data Collection

Participants were invited to take part in in‐depth individual interviews via Zoom or by phone. Each interview lasted about 30 to 40 min. Before the interview, participants completed a survey on sociodemographic information. Open‐ended questions were used to explore participants' satisfaction, awareness, knowledge, attitudes, perceptions, and practices related to pneumococcal vaccination [31]. The interviews were conducted by one facilitator with extensive experience in qualitative research, assisted by one observer/recorder. The facilitator commenced the interview and reiterated the study objectives, interview process, and the use of audio recording for research purposes. Questions outlined in the interview guide were used to facilitate discussion, and the interview content was recorded throughout. After all questions had been addressed, participants were invited to provide any additional comments.

2.3. Data Analysis

All interviews were audio‐recorded and transcribed verbatim in Chinese, adhering to a standardized transcription protocol to maintain consistency. To preserve the original meanings and minimize interpretation bias, transcripts were translated into English only after the completion of data analysis. Transcribers received training and were supervised by an experienced researcher, who also validated the transcripts to ensure accuracy and reliability. Data were analysed using thematic analysis informed by the TDF. Two experienced researchers independently coded the transcripts to identify meaningful units related to participants' perceptions, attitudes, barriers, and facilitators of pneumococcal vaccination. Preliminary codes and themes were generated inductively from participants' accounts. Coding discrepancies were resolved through discussion, with consultation with a senior researcher when necessary. The preliminary themes were then systematically revisited, refined, and mapped onto relevant TDF domains and constructs. Final findings were organised according to TDF domains and constructs, with representative quotations used to illustrate each theme.

2.4. Quality Assurance

Prior to the study, a pilot test was conducted with eligible participants to assess the clarity and appropriateness of the interview guide. The final version of the interview guide was revised to incorporate additional questions addressing new concepts or themes identified during the pilot test. Interviewers and transcribers received comprehensive training and were supervised by a senior researcher. Regular meetings were held to address difficulties encountered during the research process.

2.5. Ethical Considerations

Ethical approval for the study was granted by the Survey and Behavioural Research Ethics Committee (SBREC) of The Chinese University of Hong Kong (SBRE‐24‐0053). Written informed consent was obtained from all participants prior to their involvement in the study. All participants were clearly informed of the study's purpose, procedures, and their right to withdraw without any penalty. All data were de‐identified and stored on encrypted devices to protect participants' privacy. To enhance the response rate, each participant was offered a supermarket coupon valued at HK$100 as an incentive after the interview.

3. Results

3.1. Characteristics of the Included Participants

A total of 25 eligible individuals were approached and invited to participate in this qualitative study. Of these, one declined participation, and 24 participants were included, with six in each group. More than half of the participants expressed willingness to receive pneumococcal vaccination (n = 13, 54.2%). Overall, the majority of participants were female, accounting for 62.5% (n = 15) of all participants, while nine were male (37.5%). Most participants had a secondary school education or above (n = 17, 70.8%). More than half were retired (n = 14, 58.3%). Eighteen participants reported at least one chronic disease (75.0%). Among the reported conditions, the specific pneumococcal risk factors represented in the sample included asthma/chronic lung disease (n = 2), diabetes (n = 5), immunocompromised conditions related to cancer treatment (n = 2), chronic liver disease or fatty liver (n = 2), and chronic kidney disease (n = 1). The majority of participants reported a neutral self‐assessed health status (n = 15, 62.5%). Sociodemographic information for participants is provided in Table 1.

Table 1.

Sociodemographic characteristics of participants (n = 24).

Demographic characteristics	N (%)
1. Gender
Male	9 (37.5)
Female	15 (62.5)
2. Age (years)
18–49	6 (25.0)
50–64	6 (25.0)
≥ 65	12 (50.0)
3. Education level
Primary school or below	7 (29.2)
Secondary school	12 (50.0)
Tertiary education or above	5 (20.8)
4. Monthly household income
HKD 15,000 or below	12 (50.0)
HKD 15,001–30,000	5 (20.8)
HKD 30,001–45,000	6 (25.0)
HKD 45,001 or above	1 (4.2)
5. Marital status
Single	3 (12.5)
Married or cohabiting	15 (62.5)
Divorced/Separated/Widowed	6 (25.0)
6. Employment status
Full‐time	6 (25.0)
Part‐time	1 (4.2)
Retired	14 (58.3)
Unemployed	2 (8.3)
Homemaker	1 (4.2)
7. Residence area
Hong Kong Island	0 (0)
Kowloon	4 (16.7)
New Territories	20 (83.3)
8. Housing type
Public Housing	13 (54.2)
Subsidized Housing	2 (8.3)
Private Housing	9 (37.5)
9. Chronic disease status
None	6 (25.0)
One chronic disease	14 (58.3)
Multimorbidity	4 (16.7)
10. Specific pneumococcal risk factors represented
Asthma/chronic lung disease	2 (8.3)
Diabetes	5 (20.8)
Immunocompromised condition related to cancer treatment	2 (8.3)
Chronic liver disease or fatty liver	2 (8.3)
Chronic kidney disease	1 (4.2)
11. Self‐rated health status
Good	6 (25.0)
Neutral	15 (62.5)
Poor	3 (12.5)
12. Intention to receive pneumococcal vaccination
Yes	13 (54.2)
No	10 (41.7)
Under consideration	1 (4.2)

3.2. Barriers and Facilitators to Pneumococcal Vaccination Using TDF

Barriers and facilitators to pneumococcal vaccination were analysed using the TDF. Key themes emerged from the interviews across 12 domains: Knowledge; Social/Professional role and identity; Beliefs about capabilities; Optimism; Beliefs about consequences; Reinforcement; Intentions; Goals; Memory, attention and decision processes; Environmental context and resources; Social influences; and Emotion. No themes were identified under the Skills or Behavioural regulation domains. Table 2 provides representative quotations for each identified theme. The most frequently cited facilitators of pneumococcal vaccination were “Trust in healthcare professionals” (cited by 18 participants, 75.0%), followed by “Financial support encourages vaccination” (cited by 17 participants, 70.8%), and “Need for promotion and information regarding vaccination” (cited by 16 participants, 66.7%). Conversely, predominant barriers included “Limited understanding of pneumococcal vaccination and the vaccination programme” mentioned by 18 participants (75.0%), followed by “Strong reliance on personal judgement in vaccination decision‐making” cited by 13 participants (54.2%), and “Limited knowledge of PD” (cited by 12 participants, 50.0%). Details are presented as follows.

Table 2.

Representative quotations illustrating barriers and facilitators to pneumococcal vaccination decision‐making.

TDF domains	Facilitators	Barriers
Knowledge	Need for promotion and information regarding vaccination (n  = 16) “I think there needs to be more publicity to raise awareness of the seriousness of the disease situation.” [RALCH001] “The information needs to be more comprehensive, covering the benefits and drawbacks of this injection; we need to explain that more.” [NRF003] “The Government should do more outreach, like setting up booths to provide more information, such as where to get vaccinated, the costs, and how to qualify for free vaccination services.” [ORJY003] “Perhaps we should increase outreach to communities and strengthen publicity efforts. After all, it's only by going into the neighborhoods that we can reach those high‐risk individuals, like older adult.” [RACW006] “There has been no news coverage of this issue… More publicity is needed on television. Because citizens and the elderly rely more on information provided by television.” [ORMC006]	Limited understanding of the pneumococcal vaccination and vaccination programme (n  = 18) “I don't even know its origin or manufacturer—none of that is clear.” [NRF003] “Even now, I still don't know where to get the pneumococcal vaccine.” [RALCH001] “I don't know if the vaccine has any side effects; what benefits it offers me; or how effective it is at protecting me.” [ORDKL004] “I'm not sure what the side effects are, nor the duration of a protective effect.” [ORJY003] “I don't know much about this vaccine. I've heard of pneumococcal disease, but I've never heard of a vaccine for it.” [ORLYN002] “Should we get one dose or multiple doses? We don't know any of this, we're not informed.” [NRF001]
		Limited knowledge of pneumococcal disease (n  = 12) “I don't know. I have no idea what this pneumococcus is. It's like coughing or having weak lungs… I really don't understand this illness.” [NRF002] “I'm not familiar with pneumococcal disease… Is it related to lung cancer?” [RF002] “I don't really know it. Is it contagious?” [OECCE001] “I only know that pneumococcal disease is an illness that affects the lungs. But I haven't delved into the details.” [ORDKL004]
		Limited channels for accessing vaccination‐related knowledge (n  = 2) “Sometimes I hear about lectures for this programme, but by the time I find out about them, they've already expired, so I don't know about these lectures anymore.” [RF001] “Because there haven't been many public awareness campaigns, I don't know anything about this vaccine.” [RACW006]
Social/professional role and identity	Social and family responsibilities encourage vaccination (n  = 5) “I'm worried about infecting them (my family), and that's one of the reasons driving me to get vaccinated.” [ORJY003] “I work at a clinic, so I'm also concerned about contracting this virus.” [RACW006]
Beliefs about capabilities	Perceived risk and susceptibility to pneumococcal disease among the vulnerable population (n  = 8) “Individuals with chronic disease… have a weakened immune system and are more susceptible to infections. I have asthma…I think people like that should take up this vaccine…also for everyone (with compromised immunity).” [OECCE001]. “Because I'm getting older, my immunity is relatively low, and combined with my frequent alcohol consumption, I'm also concerned about the risk of infection.” [RAYKW003] “I worry that my immunity isn't strong enough, so I'll get this vaccine.” [ORJY003] “If pneumococcus is directly linked to pneumonia, I consider that very serious. I have lung disease, and an infection would make my daily life even more difficult.” [RAT004]	Low confidence in an individual's ability to receive vaccination (n  = 5) “I try to get as few vaccines as possible because I have a history of cancer and have been in recovery for about 20 years, so I try to avoid any other vaccines.” [ORLYN002] “I'm afraid of whether I can handle the side effects from the vaccination, and if I can't…that would be troublesome.” [RF001]
	Self‐efficacy for participation in the vaccination programme (n  = 4) “I believe I have the ability to schedule vaccinations… My own mobility is okay.” [NRF003]
Optimism	View vaccination as trustworthy and safe (n  = 4) “I believe the vaccine has undergone clinical trials. If it can be considered ready for release, I think it's okay.” [ORLYN002] “Actually, it's been available for quite some time now, so there's confidence and anticipation of its effectiveness.” [RAK005]	Lack of confidence in vaccination (n  = 1) “I'm not 100% confident about it… it's probably because it might not work for everyone.” [RF004]
Beliefs about consequences	Perceived protective benefits of pneumococcal vaccination (n  = 15) “I believe that vaccination at least protects us from being so easily infected with this pneumonia.” [RF001] “Vaccines are important because they offer protection—or rather, they don't prevent infection; even if you get infected, you won't develop a severe illness.” [RAK005]	Concerns about severe and long‐term side effects (n  = 9) “I don't know what effect invasive substances like this will have on my organs once they enter my body.” [NRF004] “I'm concerned about unknown side effects that may occur after vaccination.” [NRF002] “I'm worried that if any side effects appear after vaccination, they might be uncontrollable. If that situation arises, what should I do about this?” [RAA002]
Reinforcement	Financial support encourages vaccination (n  = 17) “If there's some financial subsidy, that would be a good incentive.” [OECCE001] “If it's free, I would be much more likely to get vaccinated because financial considerations are part of my decision‐making process.” [RAT004].	Concerns outweigh financial incentives (n  = 3) “It wouldn't increase my desire to get the shot; there's no reason to get it just for the prize.” [NRF002] “But if there's a side effect, even a subsidy, I wouldn't get it.” [ORD005] “The primary concern is effectiveness and the entire supporting infrastructure…the price is only one part of the overall concerns” [RAA002]
Intentions	Positive perception of the vaccine's effectiveness outweighs side effects (n  = 3) “If the pneumococcal vaccine really works… even if it causes a fever… I'd be happy to try it.” [OECCE001] “If pneumococcus is highly contagious or has a high incidence rate, I would get vaccinated as long as the probability of side effects is low.” [RAT004]	Perceived low importance of vaccination due to lack of urgency (n  = 6) “Most importantly, I don't need to get vaccinated right now… because this isn't a hot issue, it's not a major problem.” [ORLYN002] “I would consider getting vaccinated, but it depends on the pneumococcus before making a decision… if pneumococcus isn't prevalent in Hong Kong…I wouldn't get vaccinated even if it were free.” [ORDKL004]
		Overconfidence in personal health (n  = 1) “I am not an elderly person, so I should not need to get this vaccine.” [ORMC006]
Goals	The goal of achieving herd immunity (n  = 1) “It's for my family, myself, and also the community, because if everyone is vaccinated, fewer people will get sick, and fewer people will need to see a doctor.” [RF001]
Memory, attention and decision processes	Preference for choosing vaccine type or manufacturer (n  = 10) “I pay attention to which manufacturer produced it and where it was made… The effectiveness might not be exactly the same.” [RAYKW003] “I'll go check the vaccine first, find out which manufacturer it is, and then I'll go back and look at the manufacturer's past records… because if the manufacturer has a bad reputation, I'll avoid the vaccine produced by this manufacturer.” [RAT004] “I will consider the manufacturer's past track record and experience… I place great importance on the authenticity of vaccine data.” [ORDKL004] “I consider vaccine safety when getting vaccinated, but I haven't heard much about this particular vaccine, so I won't be getting it for now… I also look at where the vaccine is made—I have more confidence in vaccines manufactured abroad.” [RAA002]	Role of negative vaccination experience in decision‐making (n  = 1) “A long time ago… the public needed to get the COVID‐19 vaccine… I developed a fever the day after vaccination, so I won't get vaccinated again.” [NRF005]
	Role of positive vaccination experience in the decision‐making (n  = 4) “I've had flu and COVID vaccines without any adverse reactions… so I would consider getting this vaccine.” [ORJY003] “I've had no issues with other vaccines in the past, so I don't see any risk in getting the pneumococcal vaccine either.” [RF004]
	Preference for single‐dose vaccination due to convenience (n  = 4) “If it can be completed in one shot, I would be more inclined to get vaccinated because it avoids scheduling another appointment.” [RAYKW003] “A single‐dose vaccine makes the process more convenient.” [NRF003]
Environmental context and resources	Easy access and convenient booking arrangements encourage vaccination (n  = 11) “For example, parents may not want to take young children to distant locations for vaccinations, and the elderly are also reluctant to travel far for those things (vaccination). Therefore, for people in our age group, if it is accessible by transportation, this may facilitate participation.” [RAA002]. “If I could get vaccinated at the clinic where I usually visit or a nearby health centre, I would consider it.” [RF004] “It would make me more inclined to get vaccinated if it were more convenient, since you wouldn't have to spend time making an appointment, and it wouldn't be difficult to schedule one.” [RAK005]	Inconvenient service arrangements discourage vaccination desire (n  = 7) “Private clinics require appointments, which makes me less inclined to go.” [RF005] “Difficult to book, inconvenient… Actually, if I can't book the place I want, I won't go.” [RAYKW003] “Even if I am willing to pay for the pneumococcal vaccine through a private healthcare provider, they may not offer this vaccine… so I won't get the vaccination unless I really need it.” [NRF002]
		Concerns about the availability of resources to support the vaccination process (n  = 1) “Every clinic has routine tasks to handle… Do they really have sufficient resources… and time to ensure the entire (pneumococcal vaccination) process runs smoothly?” [RAA002]
Social influences	High credibility and trust in Hong Kong's healthcare system (n  = 8) “If the government recommends getting vaccinated, then I have confidence it provides protection.” [OECCE001] “As long as this vaccine can be used within Hong Kong's healthcare system, I believe it is qualified.” [ORLYN002]	Strong reliance on personal judgement in vaccination decision‐making (n  = 13) “Because my family wasn't in the medical field, they said (something about the vaccine), I just knew… But it won't push me to receive vaccination.” [ORD005]. “You decide for yourself…If I decide to get vaccinated, others' recommendations won't affect me.” [RAYKW003] “Because it was my own choice, the actions and advice of family and friends had little influence on me.” [RALCH001]
	Trust in healthcare professionals (n  = 18) “The doctor's opinion is the most important… Doctors have more medical knowledge than I do and might know about my potential health issues and the benefits of getting vaccinated.” [ORLYN002] “Because they (healthcare professionals) have a better understanding, and their network might include people related to this disease or the production of the vaccine, their credibility is comparatively higher.” [RAT004]. “Doctors possess professional expertise and are well‐informed about my health conditions” [ORDKL004]	Discouraging healthcare professional attitudes reduce motivation to vaccinate (n  = 2) “I don't feel obligated to get the shot. I wanted it before, but they (healthcare professionals) wouldn't let me get it, so it's not my problem.” [NRF002] “The family doctor who previously managed my case has retired but refuses to release my medical records, leaving me with a certain degree of disappointment and doubt regarding the doctor's integrity.” [ORD005]
	Influence of family and peers on vaccination decisions (n  = 6) “If my family asks me to go get vaccinated with them, I will go.” [OECCE001] “If my wife suggested I get vaccinated, I'd definitely go get it done.”[RF006] “I will consult my friends to determine if anyone has received the pneumococcal vaccine and to gather information regarding any effects experienced.” [NRF003] “If the pneumococcal vaccine is something everyone needs to get vaccinated, like the COVID vaccine, I'd certainly get it.” [ORMC006]
Emotion	Fear‐driven vaccination behaviour (n  = 3) “If I get infected, I might get really anxious. Because I have a history of mental illness, I often feel mentally absent and worry I might die.” [NRF006]. “The pneumococcus seems highly contagious…seeing how serious it is makes me panic and want to get vaccinated” [OECCE001] “Taking care of the lung is important. My friend just passed away a few days ago due to lung issues…it really made me realize the need to prevent lung problems.” [RF002]	Unpleasant emotional feelings towards vaccination (n  = 5) “I'm afraid of needles. Even for blood draws, just seeing the needle makes my whole body stiffen… Especially when I hear about vaccination, I already feel uncomfortable.” [NRF005] “The invasive nature of vaccination and injection concerns me greatly.” [NRF004]

Note: n denotes the number of participants mentioning each theme. Participants could contribute to more than one theme.

3.3. Knowledge

Limited awareness of PD, particularly regarding its nature, symptoms, consequences, and contagiousness, discouraged participants from receiving vaccination. Many reported having little or no understanding of the disease itself: “I don't know. I have no idea what this pneumococcus is. It's like coughing or having weak lungs… I really don't understand this illness.” [NRF002]; “I'm not familiar with PD … Is it related to lung cancer?” [RF002]; “I don't really know it. Is it contagious?” [OECCE001].

Beyond disease‐related knowledge, participants also identified substantial information gaps regarding the pneumococcal vaccination programme. Uncertainty about vaccine access, vaccine origin or manufacturer, effectiveness, and potential side effects undermined their motivation to receive pneumococcal vaccination: “Even now, I still don't know where to get the pneumococcal vaccine.” [RALCH001]; “I don't know if the vaccine has any side effects; what benefits it offers me; or how effective it is at protecting me.” [ORDKL004]. Participants further criticised the limited channels through which vaccine‐related information was disseminated, noting that inadequate publicity constrained their ability to obtain timely and relevant knowledge: “Sometimes I hear about lectures for this programme, but by the time I find out about them, they've already expired, so I don't know about these lectures anymore.” [RF001]; “Because there haven't been many public awareness campaigns, I don't know anything about this vaccine.” [RACW006].

Conversely, participants consistently emphasised the need for enhanced and more accessible outreach efforts to address these knowledge deficits. They called for clearer communication about programme logistics, the seriousness of the disease, and the benefits and potential side effects of vaccination, particularly for high‐risk groups such as older adults: “I think there needs to be more publicity to raise awareness of the seriousness of the disease situation.” [RALCH001]; “The information needs to be more comprehensive, covering the benefits and drawbacks of this injection; we need to explain that more.” [NRF003]; “The Government should do more outreach, like setting up booths to provide more information, such as where to get vaccinated, the costs, and how to qualify for free vaccination services.” [ORJY003].

3.4. Social/Professional Role and Identity

Participants described how their social and family responsibilities influenced vaccination decision‐making, particularly in relation to protecting close contacts. Concern about transmitting infection to family members was described as motivating willingness to receive vaccination: “I'm worried about infecting them (my family), and that's one of the reasons driving me to get vaccinated.” [ORJY003]. Professional roles involving higher exposure risk similarly enhanced willingness to vaccinate, especially among healthcare‐related occupations: “I work at a clinic, so I'm also concerned about contracting this virus.” [RACW006].

3.5. Beliefs about Capabilities

Perceived susceptibility to infection, shaped by ageing, chronic illness, unhealthy behaviours, and compromised immunity, emerged as a salient driver of vaccination intention. Participants associated weakened immunity with greater need for protection: “Individuals with chronic disease… have a weakened immune system and are more susceptible to infections. I have asthma…I think people like that should take up this vaccine…also for everyone (with compromised immunity).” [OECCE001]; “Because I'm getting older, my immunity is relatively low, and combined with my frequent alcohol consumption, I'm also concerned about the risk of infection.” [RAYKW003]. Similarly, participants with high self‐efficacy demonstrated positive attitudes toward receiving pneumococcal vaccination: “I believe I have the ability to schedule vaccinations… My own mobility is okay.” [NRF003]. However, individuals with health concerns and low self‐confidence expressed concerns about their ability to manage potential side effects from vaccination: “I try to get as few vaccines as possible because I have a history of cancer and have been in recovery for about 20 years, so I try to avoid any other vaccines.” [ORLYN002]; “I'm afraid of whether I can handle the side effects from the vaccination, and if I can't…that would be troublesome.” [RF001].

3.6. Optimism

Confidence in scientific evidence and societal observations reinforced participants' trust in the vaccine, ultimately motivating them to receive vaccination: “I believe the vaccine has undergone clinical trials. If it can be considered ready for release, I think it's okay.” [ORLYN002] and “Actually, it's been available for quite some time now, so there's confidence and anticipation of its effectiveness.” [RAK005]. However, residual uncertainty persisted among some participants, reflecting tempered optimism about universal efficacy: “I'm not 100% confident about it… it's probably because it might not work for everyone.” [RF004].

3.7. Beliefs about Consequences

Participants frequently highlighted the perceived protective benefits of pneumococcal vaccination, particularly its role in preventing infection and severe illness: “I believe that vaccination at least protects us from being so easily infected with this pneumonia.” [RF001]; “Vaccines are important because they offer protection—or rather, they don't prevent infection; even if you get infected, you won't develop a severe illness.” [RAK005]. Nonetheless, apprehension regarding potential side effects and uncertainty about bodily responses tempered these positive beliefs: “I don't know what effect invasive substances like this will have on my organs once they enter my body.” [NRF004]; “I'm worried that if any side effects appear after vaccination, they might be uncontrollable. If that situation arises, what should I do about this?” [RAA002].

3.8. Reinforcement

Financial support measures, including subsidies or fee waivers, were widely regarded as facilitators of willingness to receive pneumococcal vaccination: “If there's some financial subsidy, that would be a good incentive.” [OECCE001] and “If it's free, I would be much more likely to get vaccinated because financial considerations are part of my decision‐making process.” [RAT004]. However, others emphasised that cost alone was insufficient to override concerns about effectiveness, side effects, and system readiness: “It wouldn't increase my desire to get the shot; there's no reason to get it just for the prize.” [NRF002]; “The primary concern is effectiveness and the entire supporting infrastructure…the price is only one part of the overall concerns ” [RAA002], and “But if there's a side effect, even a subsidy, I wouldn't get it.” [ORD005].

3.9. Intentions

Despite awareness of potential adverse effects, many participants indicated willingness to vaccinate if effectiveness was assured or if pneumococcus was perceived as highly transmissible: “If the pneumococcal vaccinereally works… even if it causes a fever… I'd be happy to try it.” [OECCE001]; “If pneumococcus is highly contagious or has a high incidence rate, I would get vaccinated as long as the probability of side effects is low.” [RAT004]. However, perceived low disease prevalence in Hong Kong weakened perceived urgency and vaccination intention: “Most importantly, I don't need to get vaccinated right now… because this isn't a hot issue, it's not a major problem.” [ORLYN002]. Overconfidence in personal health status also contributed to vaccination reluctance: “I am not an elderly person, so I should not need to get this vaccine.” [ORMC006].

3.10. Goals

Some participants framed vaccination as a means of achieving broader collective benefits, including herd immunity and reducing healthcare burden: “It's for my family, myself, and also the community, because if everyone is vaccinated, fewer people will get sick, and fewer people will need to see a doctor.” [RF001].

3.11. Memory, Attention and Decision Processes

Decision‑making was strongly influenced by participants' desire for autonomy and informed choice, particularly regarding vaccine type, manufacturer, and data credibility: “I pay attention to which manufacturer produced it and where it was made… The effectiveness might not be exactly the same.” [RAYKW003]; “I will consider the manufacturer's past track record and experience… I place great importance on the authenticity of vaccine data.” [ORDKL004]. Preference for single‑dose regimens was also evident, reflecting efforts to minimise inconvenience: “If it can be completed in one shot, I would be more inclined to get vaccinated because it avoids scheduling another appointment.” [RAYKW003].

Additionally, participants described how prior vaccination experiences influenced individuals' future vaccination decisions. Favourable past experiences, particularly those without adverse side effects, amplified positive perceptions and increased their willingness to receive pneumococcal vaccination. For instance, two respondents stated: “I've had flu and COVID vaccines without any adverse reactions… so I would consider getting this vaccine.” [ORJY003]; “I've had no issues with other vaccines in the past, so I don't see any risk in getting the pneumococcal vaccine either.” [RF004]. In contrast, negative experiences led to vaccination avoidance: “A long time ago… the public needed to get the COVID‐19 vaccine… I developed a fever the day after vaccination, so I won't get vaccinated again.” [NRF005].

3.12. Environmental Context and Resources

Practical considerations, such as accessibility of vaccination sites and convenient appointment scheduling for the vaccination services, were described as key facilitators that promoted participation: “For example, parents may not want to take young children to distant locations for vaccinations, and the elderly are also reluctant to travel far for those things (vaccination). Therefore, for people in our age group, if it is accessible by transportation, this may facilitate participation.” [RAA002]; “It would make me more inclined to get vaccinated if it were more convenient, since you wouldn't have to spend time making an appointment, and it wouldn't be difficult to schedule one.” [RAK005].

Participants described structural barriers, including complicated appointment systems, limited availability in private settings, and concerns about system capacity, as key deterrents to vaccination: “Private clinics require appointments, which makes me less inclined to go.” [RF005]; “Even if I am willing to pay for the pneumococcal vaccine through a private healthcare provider, they may not offer this vaccine… so I won't get the vaccination unless I really need it.” [NRF002]; and “Every clinic has routine tasks to handle… Do they really have sufficient resources… and time to ensure the entire (pneumococcal vaccination) process runs smoothly?” [RAA002].

3.13. Social Influences

Participants' decision‐making was strongly influenced by healthcare professionals and government recommendations. Trust in government endorsement and the healthcare system strongly shaped positive attitudes toward vaccination: “If the Government recommends getting vaccinated, then I have confidence it provides protection.” [OECCE001] and “As long as this vaccine can be used within Hong Kong's healthcare system, I believe it is qualified.” [ORLYN002]. Likewise, healthcare professionals were widely regarded as credible authorities: “The doctor's opinion is the most important… Doctors have more medical knowledge than I do and might know about my potential health issues and the benefits of getting vaccinated.” [ORLYN002], “Because they (healthcare professionals) have a better understanding, and their network might include people related to this disease or the production of the vaccine, their credibility is comparatively higher.” [RAT004], and “Doctors possess professional expertise and are well‐informed about my health conditions” [ORDKL004]. Additionally, peer and family influence shaped vaccination decisions through shared norms and experiences: “If my family asks me to go get vaccinated with them, I will go.” [OECCE001]; “I will consult my friends to determine if anyone has received the pneumococcal vaccine and to gather information regarding any effects experienced.” [NRF003]; “If the pneumococcal vaccine is something everyone needs to get vaccinated, like the COVID vaccine, I'd certainly get it.” [ORMC006].

However, some participants stressed vaccination as an individual decision and were resistant to non‑professional influence: “You decide for yourself…If I decide to get vaccinated, others' recommendations won't affect me.” [RAYKW003] and “Because my family wasn't in the medical field, they said (something about the vaccine), I just knew… But it won't push me to receive vaccination.” [ORD005]. Moreover, discouraging or passive behaviour from healthcare providers eroded trust and reduced motivation: “I don't feel obligated to get the shot. I wanted it before, but they (healthcare professionals) wouldn't let me get it, so it's not my problem.” [NRF002]; “The family doctor who previously managed my case has retired but refuses to release my medical records, leaving me with a certain degree of disappointment and doubt regarding the doctor's integrity.” [ORD005].

3.14. Emotion

Fear of infection and anxiety about severe outcomes heightened motivation to receive vaccination: “If I get infected, I might get really anxious. Because I have a history of mental illness, I often feel mentally absent and worry I might die.” [NRF006]; “Taking care of the lung is important. My friend just passed away a few days ago due to lung issues…it really made me realize the need to prevent lung problems.” [RF002]. In contrast, fear of needles and the invasive nature of vaccination acted as psychological barriers: “I'm afraid of needles. Even for blood draws, just seeing the needle makes my whole body stiffen… Especially when I hear about vaccination, I already feel uncomfortable.” [NRF005]; “The invasive nature of vaccination and injection concerns me greatly.” [NRF004].

4. Discussion

4.1. Summary of Findings

This qualitative study examined the views of 24 adults from pneumococcal vaccination target groups in Hong Kong regarding pneumococcal vaccination. More than half of the participants indicated willingness to be vaccinated. Guided by the TDF, the study identified several key factors influencing vaccination decisions. Trust in healthcare professionals and confidence in government recommendations emerged as one of the most commonly reported facilitators of willingness to receive pneumococcal vaccination. Financial support measures, such as free or subsidized vaccination, were also considered important in encouraging participation. In addition, participants emphasized the need for clearer and more accessible information about PD and pneumococcal vaccination, including disease severity, vaccine effectiveness, side effects, eligibility, and service availability, to support informed decision‑making. The main barriers to vaccination were limited understanding of pneumococcal vaccination, strong reliance on personal judgement in vaccination decision‐making, and limited knowledge of PD. Additional barriers included concerns about vaccine safety, low perceived urgency, and practical constraints related to service accessibility and appointment arrangements. Participants’ accounts suggested that these gaps in knowledge and risk perception were associated with vaccination hesitancy, even among individuals at higher risk, highlighting the importance of targeted education and improved communication strategies to enhance pneumococcal vaccination uptake.

4.1.1. Evidence from Previous Research

Among our interviewed high‐risk individuals, 13 of the 24 participants expressed willingness to receive pneumococcal vaccination, highlighting the need for interventions to facilitate the successful implementation of a vaccination programme. Similar challenges in pneumococcal vaccination uptake and coverage have been reported in other countries. In South Korea, the national pneumococcal vaccination programme provides free PPSV23 to adults aged ≥ 65 years alongside childhood PCV10/13 immunization, while recent recommendations have been updated to allow either single‐dose PCV20 or sequential PCV15 + PPSV23 for adults aged ≥ 65 years and high‐risk adults aged 19–64 years [32]. A hospital‐based study of vaccine‐eligible adults in South Korea reported pneumococcal vaccination coverage of only 17.6%, with younger adults with chronic medical conditions consistently less likely to receive pneumococcal vaccination [33]. In Japan, routine PPSV23 vaccination is offered to adults aged 65 years and eligible high‐risk adults aged 60–64 years. A transitional catch‐up programme for selected older age groups ended in March 2024 [34]. A nationwide, web‐based cross‐sectional study conducted in March 2023 reported overall coverage of 55.1% among adults aged ≥ 65 years, but very low coverage among adults aged 19–64 ​years with chronic medical conditions (3.2%–12.4% depending on age band); a decade‐long catch‐up subsidy did not improve adult coverage, underscoring structural barriers outside the oldest age group [34].

Patients' attitudes toward pneumococcal vaccination are shaped by a combination of demographic, psychological, and contextual factors, which together influence perceived need and motivation for immunisation. In our study, the role of healthcare professionals in guiding vaccination decisions was widely recognized. Since many participants were unfamiliar with PD and pneumococcal vaccination, vaccination decision‐making relied heavily on external promotions, particularly recommendations from trusted healthcare professionals. Similarly, recent qualitative and survey studies have shown that risk appraisal, trusted recommendations, and practical access barriers are important influences on individuals' attitudes towards pneumococcal vaccination [34, 35, 36]. Country‐specific evidence further highlights the importance of external cues in shaping vaccination decisions. In Japan's national web survey, doctor recommendation (35.1%) was the top reason for vaccination among adults aged 19–64 years with chronic medical conditions, while municipal notifications (46.1%) were decisive for those aged ≥ 65 years, illustrating how programme signals may shape vaccination attitudes differently by age [34]. In the UK, focus‐group work with older adults (13 groups, n = 56) also found that vaccination decisions were influenced by previous experiences, interpersonal interactions, lack of information, and opportunities to discuss vaccines with healthcare professionals [35]. A multi‐country qualitative analysis echoed these themes, showing that older adults' perceptions of disease severity and susceptibility, information needs, misinformation, access barriers, and healthcare provider advice shaped vaccination decision‐making [36]. Health Belief Model (HBM)‐based surveys further suggested that higher perceived susceptibility and severity, perceived benefits, and strong cues to action, particularly physician recommendations, were associated with positive attitudes, while perceived barriers such as cost, access difficulty, and scepticism about vaccine safety were negatively associated [17]. In Malaysia's Klang Valley, an HBM‐based survey among older adults found that perceived seriousness, low perceived barriers, active prompts (cues to action), and trust in vaccination and healthcare providers were stronger predictors of willingness than income or formal education [37].

Furthermore, our study found that despite being unfamiliar with PD and pneumococcal vaccination, some participants recognized the perceived benefits of vaccination and expressed some confidence in vaccine safety. Consistent with this, a study of parents in Singapore found that those who intended to vaccinate their children with PCVs were more aware of PD, better understood the vaccine's protective benefits, and were more likely to know it was officially recommended, compared to those who were unwilling [38]. The effectiveness of PCVs and PPSV23 in preventing IPD and NIPD was consistently supported by evidence from randomized controlled trials and systematic reviews [39, 40, 41, 42, 43]. The CAPITA randomized controlled trial demonstrated that PCV13 reduced vaccine‐type community‐acquired pneumonia (VT‐CAP) by 46%, VT non‐bacteremic pneumonia by 45%, and vaccine‐type invasive pneumococcal disease (VT‐IPD) by 75% in adults aged 65 years or older [39]. A systematic review of adult studies estimated PPSV23 effectiveness at about 45% for PPSV23‐type IPD and 18% for PPSV23‐type pneumococcal pneumonia [40]. Furthermore, another systematic review of conjugate vaccines reported substantial declines in childhood pneumonia‐related outcomes following PCV10 or PCV13 introduction, with pneumococcal‐confirmed pneumonia reductions of 45%–85% and radiologically confirmed pneumonia reductions of 12%–79% [41]. Safety assessments across decades of research show that pneumococcal vaccines have generally shown acceptable safety profiles. A systematic review of 42 studies concluded that pneumococcal vaccines were generally well tolerated, with mostly mild and transient adverse events such as injection‐site pain or low‐grade fever, and no major safety concerns identified [42]. More recent meta‐analysis evidence of PCV15 trials indicated higher rates of local and systemic reactions compared with PCV13, with risk ratios of 1.23 and 1.15, respectively, while rates of serious adverse events were comparable [43].

Beyond reported facilitators of willingness to receive pneumococcal vaccination, our study also summarized concerns that discouraged individuals from receiving pneumococcal vaccination. Financial support was one of the most commonly cited facilitators of willingness to receive pneumococcal vaccination among our participants. This suggests that financial considerations may play an important role in individuals' vaccination decisions. Similarly, a previous HBM study also found that perceived barriers, including cost, access difficulty, and scepticism about vaccine safety, were negatively associated with willingness to receive pneumococcal vaccination [17]. Therefore, the Government should carefully evaluate whether financial barriers remain among target populations and ensure that eligible individuals are aware of and able to access existing free or subsidised pneumococcal vaccination services. Moreover, a lack of awareness and information was frequently reported by our participants, which led to hesitancy in their vaccination decisions. Evidence on non‐National Immunization Programme vaccines, including PCV, has similarly identified low vaccine awareness, affordability, and concerns about vaccine safety and efficacy as key barriers to uptake [44]. The reported limited knowledge of PD and pneumococcal vaccination underscored the importance of educational interventions to improve public awareness and knowledge of PD prevention. A randomized controlled trial in the US revealed that a simple, low‐literacy educational handout significantly increased pneumococcal vaccination uptake. Patients encouraged to “ask your doctor about the pneumonia shot” were 4 times more likely to discuss the vaccine with their physicians and over 5 times more likely to receive it than the control group [45]. Given this identified barrier, the development and implementation of a targeted educational campaign might be a potential strategy for mitigating knowledge gaps and improving pneumococcal vaccination coverage.

Importantly, a clear distinction should be drawn between determinants that appear more specific to pneumococcal vaccination and those reflecting general attitudes toward adult vaccination. On one hand, the marked lack of disease awareness and low perceived susceptibility observed in our cohort appear particularly relevant to pneumococcal vaccination. This aligns with findings from qualitative and observational studies among older and at‐risk adults, which consistently highlight limited awareness and information needs regarding pneumococcal disease and vaccination [34, 36]. Unlike seasonal influenza or COVID‐19, which benefit from greater public visibility and routine vaccination campaigns [46], pneumococcal disease remains poorly understood, leading many individuals to underappreciate their personal risk unless prompted by direct clinical advice [34, 36]. On the other hand, factors such as reliance on physician recommendations, sensitivity to out‐of‐pocket costs, and accessibility barriers may reflect broader behavioural drivers documented across adult vaccination more generally [17, 20]. Distinguishing these determinants helps clarify that structural measures, such as financial subsidies and provider prompts, may support adult vaccination uptake more broadly [20, 37], whereas dedicated educational efforts are needed to address the specific knowledge and risk‐perception gaps surrounding pneumococcal disease and vaccination [36, 45].

4.1.2. Implications

The findings from this study could provide several strategic directions to enhance willingness to receive pneumococcal vaccination. Our participants demonstrated pronounced trust in healthcare professionals, which underscores their critical role in guiding patients towards vaccination. Strengthening healthcare professionals' engagement in vaccination recommendation during routine clinical encounters may represent a promising strategy for supporting vaccination decisions and potentially improving pneumococcal vaccination uptake. To facilitate their communication with patients, targeted training programmes may be developed and provided to all healthcare workers. Moreover, many of our participants emphasized financial support as a crucial facilitator of pneumococcal vaccination willingness. Therefore, to overcome this key structural barrier, policymakers should review the accessibility, eligibility criteria, awareness, and adequacy of existing funding or subsidy programmes for the vaccine, as financial support was consistently identified as a pivotal facilitator not only for pneumococcal vaccination, but also for other vaccinations. Many participants reported that they were not well‐informed about PD or pneumococcal vaccination. Consequently, sustained public health education campaigns should move beyond general vaccine promotion and provide pneumococcal‐specific information on disease severity, personal susceptibility, vaccine benefits, eligibility criteria, schedules, costs, and service arrangements. Finally, the Government and health authorities should use official media channels to proactively disseminate information on vaccine safety and efficacy based on the latest evidence, as many of our participants expressed concerns over vaccine safety and side effects. More general vaccination‐related concerns, such as safety concerns, accessibility barriers, and trust in professional recommendations, should also be addressed through clear, consistent, and authoritative communication. The existence of misinformation also needs to be addressed through appropriate policies and public communication strategies. A coordinated strategy that integrates provider advocacy, financial support, public education, and authoritative communication is therefore essential to facilitate pneumococcal vaccination uptake.

4.1.3. Strengths & Limitations

The reliability of our findings is strengthened by our adequate sample size, with 24 participants, which is robust for a qualitative study. Our sample size was large enough to capture a comprehensive range of themes and perceptions regarding pneumococcal vaccination. The qualitative design enabled an in‐depth exploration of participants' experiences, perceptions, and decision‐making processes, providing rich contextual insights that may not be captured through quantitative approaches alone. Furthermore, the use of the TDF, a rigorous methodological approach that has been widely used, ensured a systematic and theoretically informed exploration of factors influencing vaccination willingness. The TDF‐based approach enabled barriers and facilitators to be organized across behavioural domains, thereby providing practical insights for the development of future interventions. In addition, the inclusion of younger and middle‐aged adults with pneumococcal risk factors broadened the perspectives captured in this study. However, several limitations need to be considered while interpreting the findings. Firstly, our sampling approach may introduce sampling bias, as the majority of participants were recruited from the New Territories, with no participants from Hong Kong Island. This may limit the generalizability of the findings to other geographical and sociodemographic settings in Hong Kong. Secondly, as with all studies reliant on self‐reporting, the potential for social desirability bias exists. Participants may have provided responses they perceived as socially acceptable or aligned with mainstream medical advice, potentially leading to an overreporting of their true willingness to receive pneumococcal vaccination. Most importantly, the cross‐sectional and qualitative nature of this study is an inherent limitation. While it is highly effective for identifying and exploring a wide array of potential influencing factors, this design does not allow causal relationships to be established. The fact that certain factors, such as financial support, were more frequently mentioned by participants does not necessarily mean they are more important determinants of vaccination behaviour than other less reported factors. The relative importance of these factors and their definitive causal relationships with pneumococcal vaccination uptake should be examined in future quantitative and longitudinal studies.

5. Conclusion

This qualitative study explored factors influencing pneumococcal vaccination decision‐making among Hong Kong's at‐risk population. Participants reported that trust in healthcare professionals, confidence in government recommendations, financial support, and perceived benefits of pneumococcal vaccines facilitated willingness to receive vaccination. On the other hand, limited knowledge, information, and familiarity with PD and pneumococcal vaccination discouraged participants from receiving pneumococcal vaccination. Education campaigns are needed to improve public awareness and knowledge of PD and pneumococcal vaccination. Improving awareness of and access to existing free or subsidised pneumococcal vaccination services may help address financial and informational barriers. Future quantitative and longitudinal studies are warranted to further examine the relative importance of these factors and their associations with actual vaccination behaviours.

Author Contributions

Claire Chenwen Zhong: conceptualization, supervision, writing – original draft. Mingtao Chen: writing – original draft. Man Kin Yim: formal analysis, data curation. Sammi Ng: data curation, formal analysis. Junjie Huang: writing – review and editing, conceptualization, supervision. Martin C S Wong: supervision, conceptualization, writing – review and editing.

Ethics Statement

The Survey and Behavioural Research Ethics Committee of the Chinese University of Hong Kong approved the study (approval no. SBRE‐24‐0053). All participants provided written informed consent before taking part in the study.

Conflicts of Interest

The authors declare no conflicts of interest.

Transparency Statement

The corresponding authors, Junjie Huang and Martin CS Wong, affirm that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained. All authors have read and approved the final version of the manuscript. Junjie Huang and Martin CS Wong had full access to all of the data in this study and take complete responsibility for the integrity of the data and the accuracy of the data analysis.

Data Availability Statement

The qualitative data generated and analysed during the current study are not publicly available due to the sensitive nature of the data and the need to protect participant confidentiality. No additional data are available.