Prevalence and factors associated with hepatitis B vaccine uptake among undergraduate medical students in Tanzania: A cross-sectional study

Abstract

Background

Hepatitis B virus remains a major global public health concern, responsible for significant morbidity and mortality due to complications such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Hepatitis B virus prevalence remains high in many developing countries, including Tanzania, where it is estimated to be 7.17%. Medical students are particularly vulnerable to hepatitis B virus infection because of occupational exposure, including needle-stick injuries and contact with infected blood or body fluids during clinical training. Vaccination is the most effective preventive measure against hepatitis B virus infection; however, vaccine coverage among medical students remains suboptimal.

Objective

This study aimed to assess hepatitis B virus vaccine uptake and identify factors influencing vaccination among medical students in Tanzania to inform strategies for improving vaccination coverage.

Methods

An analytical cross-sectional study was conducted from March to May 2025 among undergraduate clinical-year medical students at Muhimbili University of Health and Allied Sciences in Dar es Salaam, Tanzania, to assess hepatitis B virus vaccine uptake and its associated factors. A total of 343 students participated in the study. Data were collected using a structured questionnaire. Descriptive statistics were used to determine vaccination coverage, and regression analysis was performed using Statistical Package for the Social Sciences (International Business Machines Corporation) version 28 to identify factors associated with vaccine uptake. Ethical approval was obtained from the Muhimbili University of Health and Allied Sciences Institutional Review Board, and written informed consent was obtained from all participants before data collection. Participants’ confidentiality and anonymity were ensured throughout the study.

Results

Among the 343 participants, most were aged 20–24 years (61.8%), were male (65.0%), and were in their fifth (final) year of study (53.4%). Overall, 78.1% had received at least one dose of the hepatitis B vaccine, but only 42.2% had completed the full vaccination schedule. The main reason for incomplete vaccination was awaiting subsequent doses (75%). Approximately all students (98%) had been informed about the importance of hepatitis B vaccination. Multivariable analysis showed that female sex (adjusted odds ratio = 1.99, p = 0.014), prior information about the importance of vaccination (adjusted odds ratio = 3.35, p = 0.004), previous hepatitis B testing (adjusted odds ratio = 3.14, p < 0.001), and fear of contracting hepatitis B (adjusted odds ratio = 2.39, p = 0.028) were independently associated with vaccine uptake.

Conclusion

Hepatitis B virus vaccine uptake among medical students was significantly associated with vaccine awareness, perceived risk of infection, and prior hepatitis B testing, whereas scheduling conflicts, vaccine cost, and vaccine unavailability acted as barriers to vaccination. Strengthening awareness and addressing structural barriers are important for improving vaccination coverage.

Background

Hepatitis B is a viral illness that causes acute infection and chronic conditions, including cirrhosis and hepatocellular carcinoma. It accounts for a significant proportion of the global burden of disease and mortality. ¹ The virus is responsible for approximately 300 million chronic illnesses globally and approximately 1 million deaths annually from consequent complications, such as liver cirrhosis and hepatocellular carcinoma, and is considered to be 100 times more infectious than the human immunodeficiency virus (HIV).^2,3

The global prevalence of hepatitis B virus (HBV) infection varies greatly between countries and is lower in developed countries than in developing countries. The World Health Organization (WHO) estimates that two billion people have current or past HBV infection symptoms. ¹ HBV imposes the second-highest burden in Africa after the Western Pacific region, with approximately 1.5 million new infections occurring annually, predominantly among young adults. Tanzania is classified as a highly endemic setting, with an estimated HBV prevalence of 7.17%. ³

HBV is a highly infectious pathogen transmitted through exposure to infected blood, semen, and other body fluids. Transmission may occur perinatally from infected mothers to their infants at birth as well as horizontally during early childhood through close contact with infected household members or between children.^4,5 Undergraduate medical students worldwide, particularly those in Tanzania, are at risk of acquiring HBV infection because they are exposed to infected patients and body fluids during their clinical training.^2,3

The HBV vaccine is available as a monovalent formulation administered in a standard three-dose schedule at 0, 1, and 6 months. This vaccination regimen has been demonstrated to be both safe and highly effective in preventing infection when given before exposure or shortly after exposure to the virus. Evidence further shows that vaccine-induced protection can persist for at least 35 years. Consequently, the vaccine has been incorporated into immunization programs in more than 190 countries worldwide, including Tanzania. ⁶ The WHO indicates this as a primary preventive strategy for control of the infection among healthcare workers (HCWs) and medical students^7,8 as well as Center for Disease Control and Prevention (CDC), which includes it among the recommended vaccines for HCWs and medical students. ⁹ Unfortunately, HBV vaccine coverage remains low among medical students. Therefore, this study sought to measure the gap causing this discrepancy by looking into factors influencing HBV vaccine uptake among medical students in Tanzania.

Methods

Study design, population, and study area

This study employed an institution-based cross-sectional design involving medical students at Muhimbili University of Health and Allied Sciences (MUHAS) in Dar es Salaam, Tanzania. MUHAS is a higher learning institution that enrolls both undergraduate and postgraduate students in a wide range of health-related disciplines. The university has the capacity to host more than 3800 students from various parts of Africa. It offers diverse academic programs at the national and international levels, including Doctor of Medicine, Nursing, Doctor of Dental Surgery, Pharmacy, Medical Laboratory Sciences, Environmental Health Sciences, and other related fields.

Inclusion criteria

Participants were eligible for inclusion if they met the following criteria:

1. Were medical students in the clinical years of the Doctor of Medicine program during the study period;

2. Students who provided written informed consent to participate in the study.

Exclusion criteria

Students were excluded from the study because of the following:

1. Were not present during the period of data collection;

2. Submitted incomplete questionnaires.

Sample size

The calculated minimum sample size for this study was 273, assuming a 95% confidence level (CI), a 5% margin of error, a 10% nonresponse rate, and an HBV vaccine uptake proportion of 20.2% based on a study conducted in Kenya. ¹⁰ The sample size was calculated using the following formula:

N = Z²p(1−p)/ℇ²

where N = sample size; Z = standard normal deviation at 95% CI of 1.96; p = 20.2%; ℇ = margin of error estimated to be 0.05.

Then, n = 1.96² × 0.202(1 − 0.202)/(0.05)² = 248; 10% nonresponse, n = 25. The minimum sample size for this study was 273.

Sampling technique

Participants were selected using a stratified random sampling technique. Students were stratified according to their year of study (fourth year and fifth year). The sampling frame consisted of all registered fourth- and fifth-year medical students undertaking clinical rotations during the study period. Official student registration lists were obtained from the university administration, with separate lists for each academic year. The total sample size was allocated proportionally according to the number of students in each academic year. Students were assigned unique identification numbers, and participants were selected using a computer-generated random number sequence, ensuring that all eligible students had an equal chance of selection.

Study variables

Dependent variable: Hepatitis B vaccination status.

Independent variables: Age (years), sex, health insurance coverage for the vaccine, prior HBV testing, perceived knowledge of HBV, and fear of contracting HBV infection.

Data collection

The study used a self-developed structured questionnaire designed based on the study objectives and a review of the literature on hepatitis B vaccine uptake and associated factors. Before data collection, the questionnaire was pretested among 20 medical students from the same classes who were not included in the final study. The pretest was conducted to assess the clarity, relevance, comprehensibility, and appropriateness of the questionnaire items. Feedback obtained during the pretesting process was used to refine the wording and sequencing of the questions, resulting in the final version of the questionnaire used for data collection. Data were collected between 1 March 2025 and 31 May 2025.

Data analysis and reporting

The data were checked for accuracy and completeness. Data cleaning was performed, and the data were analyzed using Statistical Package for the Social Sciences (SPSS) version 28 (IBM Corporation; USA). The prevalence of hepatitis B vaccine coverage was summarized using descriptive statistics, including counts and percentages. Bivariate analysis was conducted to assess the association between sociodemographic variables and vaccine uptake. Variables with a p value <0.05 in the bivariate analysis were entered into a multivariable regression model. Multivariable logistic regression analysis was then performed to identify factors independently associated with HBV vaccine uptake while controlling for potential confounders. The strength of associations was reported using odds ratios (ORs) with 95% CI. To test for multicollinearity, tolerance values and variance inflation factors (VIFs) were calculated for all independent variables. Multicollinearity was considered a concern if the tolerance was <0.10 or the VIF was >5. Variables with a p value <0.05 in the multivariable model were considered statistically significant. This study is reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. ¹¹

Ethical clearance

Ethical clearance to conduct the study was sought from the Muhimbili University of Health and Allied Sciences Institutional Review Board (Approval Number: DA.282/298/02L/427) on 31 December 2024. Written informed consent was obtained from each participant before data collection, and all participant information was deidentified. This study was conducted in accordance with the Declaration of Helsinki (1975), as revised in 2024.

Results

The study enrolled 343 medical students. Most participants were aged 20–24 years (212, 61.8%). Males constituted the majority of the sample (223, 65.0%), and over half of the respondents were in their final year of study (183, 53.4%). Additionally, 108 participants (31.5%) reported a monthly family income exceeding 1,000,000 Tanzanian shillings (TZS). More than half of the students (198, 57.7%) indicated that they did not have health insurance coverage for the HBV vaccine (Table 1).

Table 1.

Demographic characteristics of study participants (n = 343).

Variable (s)	Frequency (n)	Percentage (%)
Age group (years)
20–24	212	61.8
25–29	124	36.2
≥30	7	2
Mean age	24 years
SD	1.8
Sex
Male	223	65.0
Female	120	35.0
Year of study
Year 4	160	46.6
Year 5	183	53.4
Approximate monthly family income (TZS)
<200,000	68	19.8
200,000–500,000	100	29.2
500,001–1,000,000	67	19.5
>1,000,000	108	31.5
Health insurance coverage of hepatitis B vaccine
Yes	70	20.4
No	198	57.7
I do not know	75	21.9

TZS: Tanzanian shilling.

Hepatitis B vaccination status

The study found that most participants had received the HBV vaccine, with 268 (78.1%) reporting receipt of at least one dose. Among those vaccinated, 120 (44.8%) had received two doses, whereas 113 (42.2%) had completed the full three-dose schedule. More than half of the vaccinated participants had received only a partial vaccination series, whereas 116 (51%) completed the recommended vaccination schedule and 38 (17%) reported missing scheduled doses. The most frequently cited reason for not completing the vaccination series was waiting for the next scheduled dose (116, 75%). The majority of participants received the vaccine after enrolling at the university (241, 89.9%), whereas only a small proportion had been vaccinated before university entry (27, 10.1%) (Table 2).

Table 2.

Hepatitis B vaccination status.

Variable(s)	Frequency (n)	Percentages (%)
Received hepatitis B vaccine
No	75	21.9
Yes	268	78.1
Number of dose of hepatitis B vaccine received
Only one Hepatitis B vaccine dose	35	13.1
Two hepatitis B vaccine doses	120	44.8
Full vaccination (three doses)	113	42.2
Unvaccinated	75	33
Partial vaccination on schedule	116	51
Partial vaccination missed appointments	38	17
Reasons for not receiving full hepatitis B vaccine
Busy schedule	23	15
High cost	11	7
Unavailability	2	1
Lack of interest	0	0
Fear of side effects	2	1
Waiting for the next dose	116	75
Timing of hepatitis B vaccination
Before joining university	27	10.1
After joining university	241	89.9

Reasons for not receiving hepatitis B vaccine

The study identified the cost of the HBV vaccine as the most frequently reported reason for not being vaccinated (26, 25%). Other notable barriers included vaccine unavailability (18, 17%) and lack of motivation (25, 24%). A smaller proportion of participants reported fear of potential side effects (11, 11%), a busy schedule (12, 12%), lack of awareness about the vaccine (9, 9%), and the perception that vaccination was unnecessary (3, 3%) (Figure 1).

Figure 1.

Reasons for not receiving hepatitis B vaccine.

Factors associated with hepatitis B vaccine uptake

Regression analysis identified several significant predictors of HBV vaccine uptake. In the univariate analysis, female participants were more likely to receive the vaccine compared with males (crude odds ratio (COR) = 1.95, 95% CI: 1.08–3.49, p = 0.026), and this association remained significant after adjustment in the multivariable model (adjusted odds ratio (AOR) = 1.99, 95% CI: 1.79–4.95, p = 0.014).

Being informed about the importance of the vaccine was also a significant predictor in both analyses. Participants who had been informed were significantly more likely to receive the vaccine (univariate COR = 0.10, 95% CI: 0.02–0.55, p = 0.008; multivariable AOR = 3.35, 95% CI: 1.46–7.66, p = 0.004). Similarly, having previously been tested for hepatitis B infection was strongly associated with vaccine uptake (univariate COR = 1.45, 95% CI: 1.23–3.12, p < 0.001; multivariable AOR = 3.14, 95% CI: 1.39–7.12, p < 0.001).

Fear of contracting hepatitis B was another significant factor in both the univariate (COR = 1.25, 95% CI: 1.19–3.57, p < 0.001) and multivariable analyses (AOR = 2.39, 95% CI: 1.10–5.19, p = 0.028). In addition, other motivations for vaccination were significantly associated with vaccine uptake in the univariate analysis (COR = 1.21, 95% CI: 1.02–2.75, p = 0.004) and remained significant after adjustment in the multivariable model (AOR = 1.12, 95% CI: 1.11–1.32, p = 0.013). Multicollinearity was not a concern in this analysis as all tolerance values were above 0.10 (ranging from 0.49 to 0.90) and all VIFs were below 5 (ranging from 1.11 to 2.03) (Table 3).

Table 3.

Factors associated with hepatitis B vaccine uptake.

Predictor(s)	Univariate analysis		Multivariate analysis
	COR (95% CI)	p value	AOR (95% CI)	p value
Age
20–24	3.13 (0.67–14.52)	0.145	0.22 (0.03–1.60)	0.136
25–29	2.25 (0.48–10.61)	0.306	0.42 (0.06–3.10)	0.397
≥30	Ref
Sex
Male	Ref
Female	1.95 (1.08–3.49)	0.026	1.99 (1.79–4.95)	0.014
Health insurance coverage of hepatitis B vaccine
Yes	1.91 (1.05–3.49)	0.054	0.57 (0.23–1.4)	0.224
No	2.27 (1.03–5.0)	0.041	0.37 (0.12–1.14)	0.086
I do not know	Ref
Been informed about importance of HBV vaccine
Yes	0.10 (0.02–0.55)	0.008	3.35 (1.46–7.66)	0.004
No	Ref
Perceived knowledge about HBV infection and prevention
Excellent	3.17 (0.50–19.84)	0.218	0.18 (0.11–3.10)	0.238
Good	2.50 (0.40–15.60)	0.327	0.26 (0.02–4.17)	0.344
Fair	0.61 (0.09–4.34)	0.626	2.52 (0.13–48.55)	0.538
Poor	Ref
Tested for HBV infection
Yes	1.45 (1.23–3.12)	0.000	3.14 (1.39–7.12)	0.000
No	Ref
Peers who received hepatitis B vaccine
Yes	0.54 (0.19–1.49)	0.233	0.36 (0.08–1.67)	0.195
No	ref
Family influence
Yes	0.51 (0.23–1.12)	0.095	1.95 (0.67–5.69)	0.222
No	ref
University campaigns
Yes	0.59 (0.35–0.99)	0.045	0.74 (0.33–1.65)	0.466
No	ref
Personal knowledge about hepatitis B
Yes	0.42 (0.24–0.71)	0.001	1.95 (0.89–4.29)	0.094
No	ref
Fear of contracting hepatitis B
Yes	1.25 (1.19–3.57)	0.000	2.39 (1.10–5.19)	0.028
No	ref

CI: confidence interval; COR: crude odds ratios; HBV: hepatitis B virus; AOR: adjusted odds ratio; Ref: reference.

Discussion

This study explored the prevalence of HBV vaccine uptake and the factors associated with vaccine uptake among medical students in Tanzania.

The study revealed that 78.1% of participants had received at least one dose of the HBV vaccine, whereas only 42.2% had completed the full three-dose regimen. This suggests that although vaccine initiation is relatively high, the rate of complete immunization remains suboptimal. Similar patterns have been observed in other low- and middle-income countries (LMICs). For instance, a study conducted in Mogadishu, Somalia, showed that 63.1% of the sample population had received at least one dose of the HBV vaccine, whereas only 33.4% of health science students had completed the full vaccination schedule. ¹ Similarly, a study conducted in Pakistan in 2024 reported that although 66% of medical students had received the HBV vaccine, only 17.2% had completed the full three-dose series. ⁹ Comparable findings were observed in a 2021 study conducted among clinical students in southeastern Nigeria, in which 27.5% had received the vaccine and, among them, only 44.9% had completed all three doses. ¹²

In contrast, studies conducted in middle- and high-income countries have reported substantially higher vaccination completion rates. For instance, a study conducted in Greece in 2016 among medical, nursing, and paramedical students showed an overall vaccination rate of 83%, with the highest coverage among medical students (88.1%). ¹³ Similarly, a study conducted at the University of the Witwatersrand in Johannesburg, South Africa, found that 89.1% of medical students had been vaccinated against HBV, and 78.2% of those vaccinated had completed the full three dose of vaccine. This high vaccination rate was attributed to university guidelines requiring HBV vaccination for all health science students during their first year. ² The higher uptake in developed countries is often attributed to better healthcare infrastructure, mandatory vaccination policies, and more consistent access to healthcare services.

Among participants who had initiated but not completed the vaccination series, the most predominant one was being on schedule and waiting for the next dose. Other reported reasons included busy academic schedules, the high cost of the vaccine, and vaccine unavailability. These findings suggest that most students intended to complete the three-dose series but were hindered by logistical or structural constraints rather than vaccine hesitancy. These barriers are consistent with findings from other LMICs. For instance, a study conducted at a Medical Training College in Kenya reported that the main reasons for not having had full vaccination were vaccine unavailability of the vaccine when they went for it and that the vaccine dose was not yet due. ¹⁰ Similarly, a study conducted in Nigeria, showed that busy schedules, vaccine unavailability, and vaccine cost were the main barriers to completing HBV vaccination. ¹² These findings contrast with those from high-income countries, where structured immunization programs and reminder systems help ensure timely completion of vaccination schedules. ²

Among unvaccinated respondents, the most commonly reported reasons were cost of the vaccine, lack of motivation, vaccine unavailability, and busy schedules. Fear of side effects and lack of awareness about the vaccine were the least cited reasons. These findings suggest that, beyond logistical issues, motivational and informational barriers persist among medical student populations. A similar cross-sectional study conducted in Somalia among medical students showed that the main reasons for not being vaccinated included unavailability of the vaccine and high vaccine cost as the most cited reasons. At the time of our study, HBV vaccination was not routinely subsidized by the university or through a dedicated Ministry of Health program for clinical-year medical students, requiring students to pay for vaccination themselves. This context may help explain why vaccine cost emerged as an important barrier to vaccine uptake in our study. Other reported reasons included fear of vaccine side effects, lack of trust in vaccine quality, lack of awareness of where to receive vaccination, and lack of time. ¹⁴ Similar reasons were reported in studies conducted in Ghana ¹⁵ at Makerere University College of Health Sciences ¹⁶ and in Nigeria. ¹²

Female students were significantly more likely to have received the HBV vaccine compared to male students. This finding suggests a nearly twofold higher likelihood of vaccine uptake among female students. The observed difference may stem from greater health-seeking behavior, higher perceived vulnerability, or increased engagement with preventive healthcare practices among female students compared to males. Similar sex-based disparities have been noted in previous studies conducted in both developing and developed countries. For instance, research conducted at the University of Dodoma, Tanzania, at Makerere University College of Health Sciences, and a systematic review of HBV vaccination coverage in China reported higher vaccine uptake among female students, which was attributed to stronger adherence to health campaigns and more proactive attitudes toward health-seeking behaviors.^17,18

Students who had been informed about the importance of the HBV vaccine were significantly more likely to be vaccinated than those who had not been informed. This highlights the critical role of awareness and health education in vaccine uptake. Providing information likely enhances knowledge, corrects misconceptions, and motivates students to act upon perceived susceptibility to infection. These findings align with previous studies in Nigeria and at a federal University in Brazil, where educational interventions significantly improved vaccination rates among healthcare trainees.^19,20

Participants who had previously been tested for HBV infection were three times more likely to be vaccinated compared to those who had not been tested. This association may be explained by the possibility that individuals who undergo testing also receive counseling or vaccination as part of the preventive continuum. Moreover, testing may elevate an individual's perceived risk, prompting protective action such as vaccination. Similar associations have been reported in studies conducted in Ethiopia, Uganda, and USA.^21–23

Fear of contracting the infection was another significant predictor of vaccine uptake. Perceived severity and susceptibility to infection posits that individuals engage in preventive health behaviors when they perceive a serious risk. Findings from Medical College in Nepal and Northwestern Ethiopia have similarly demonstrated that heightened risk perception positively influences vaccine compliance among healthcare students.^7,22

Strengths and limitation

This study has several strengths, including its focus on medical students in their clinical rotation years, who are at increased risk of occupational exposure to HBV infection. In addition, achieving the calculated sample size adds power of the study. However, some limitations should be considered when interpreting the findings. The cross-sectional design limits the ability to establish causal relationships between the identified factors and HBV vaccine uptake. Furthermore, vaccination status and other study variables were self-reported and may therefore be subject to recall and social desirability bias. Finally, the study was conducted at a single institution, which may limit the generalizability of the findings to other medical student populations.

Conclusion

The results revealed that although a relatively high proportion of students (78.1%) had received at least one dose of the HBV vaccine, only 42.2% had completed the recommended three-dose regimen, reflecting suboptimal full immunization coverage. Female sex, being informed about the importance of HBV vaccination, having undergone HBV testing, and fear of contracting the infection may be associated with increased vaccine uptake. Barriers to vaccination may include scheduling conflicts, vaccine cost, and vaccine unavailability.