Trends in COVID-19 Vaccine Acceptance in Spain, September 2020‒May 2021

Abstract

Objectives. To analyze factors associated with COVID-19 vaccine acceptance in Spain, over time.

Methods. We used data from a national study that included 5 online surveys carried out every 2 months from September 2020 to May 2021. Each round recruited a sample of 1000 participants aged 18 years or older. We performed a multivariable logistic regression with vaccination acceptance as the dependent variable. We evaluated time trends through the interaction terms of each of the explanatory variables and the time.

Results. Vaccination acceptance increased from 43.1% in September 2020 to 84.5% in May 2021. Sex, age, concerns about disease severity, health services overload, and people not wearing a face mask, together with adherence to preventive behavior, health literacy, and confidence in scientists, health care professionals’ information, and adequacy of governmental decisions, were variables associated with vaccination acceptance.

Conclusions. In a changing situation, vaccine acceptance factors and time trends could help in the design of contextualized public health messages. It is important to strengthen the population’s trust in institutions, health care professionals, and scientists to increase vaccination rates, as well as to ensure easy access to accurate information for those who are more reluctant. (Am J Public Health. 2022;112(11):1611–1619. https://doi.org/10.2105/AJPH.2022.307039)

COVID-19 has become a global health pandemic with more than 171 049 741 cases and 3 549 710 deaths reported worldwide at the time of this study in May 2021.¹

Vaccination is one of the most cost-effective health interventions to prevent most infections. Since COVID-19 vaccination started in the European Union (EU) in December 2020, the cumulative vaccine uptake in adult population reached up to 51.2% with at least 1 vaccine dose and 26.8% with full vaccination.² However, only 5.7% of the world’s population had been fully vaccinated against COVID-19 by May 2021³

Spain is now one of the leading countries in COVID-19 vaccination adherence with 93% of the population aged 12 years or older fully vaccinated.⁴ The country started vaccinating in late December 2020 and accelerated its vaccination efforts in early 2021, overtaking countries that had made better progress earlier, like the United States and the United Kingdom.⁵ At that time, Spanish vaccination strategy focused on vaccinating the largest number of people possible with 2 doses, instead of a single dose as other countries prioritized.² At the time of this study, in May 2021, Spain had administered at least 1 COVID-19 vaccine dose to nearly 40% of its population, and more than 20% had received 2 doses.⁴

Vaccine hesitancy is defined by World Health Organization (WHO) as “delay in acceptance or refusal of vaccines despite availability of vaccination services”^6(p7) Vaccine hesitancy and misinformation are major obstacles to achieve a high vaccine coverage. COVID-19 vaccination is one of the measures for controlling the pandemic and reducing infection risk, disease severity, and mortality.⁷ Therefore, it is of great importance to understand peoplés willingness to be vaccinated.⁸

Individual and context determinants influence immunization behavior.⁸ Knowledge and risk perception are frequently described as key factors in protective behavior adherence.⁹ Similarly, concerns, misperceptions, and prejudices can also negatively affect vaccination decisions and practices.¹⁰ These insights are critical to understand individual reasons behind vaccine acceptance and to designing effective messages to achieve positive outcomes.¹¹

Health authorities have a critical role in vaccination support and promotion, ensuring equitable access to vaccination services and updated science-based information,⁸ while mass media play an important role in risk communication, avoiding unfounded discussions, misinformation, and fake news.¹² A high level of confidence in institutions and science to address the challenges created by the COVID-19 pandemic usually implies more vaccine acceptance.¹³ Studying population knowledge, attitudes, practices, and concerns about COVID-19 vaccination becomes essential in a long-term pandemic. The aim of this study was to analyze the factors associated with COVID-19 vaccination intention and its time trends. This information will be very useful for designing adequate public health messages addressed at clarifying the population’s doubts, fighting misinformation, and promoting vaccination.

METHODS

The COVID-19 Snapshot Monitoring study survey in Spain (COSMO-Spain) is based on the WHO tool for behavioral insights on COVID-19,¹⁴ carried out in different countries worldwide. This protocol has been used to conduct periodic surveys on knowledge, attitudes, and practices throughout the pandemic in Spain.¹⁵ Questionnaire details can be found on the COSMO-Spain homepage¹⁶ and in the COSMO-WHO repository.¹⁴

Setting and Study Population

We conducted analyses with data from the September 2020 to May 2021 COSMO-Spain study¹⁶ (Figure 1), including the periods between the second and fourth country epidemic waves. A consumer research company carried out 5 cross-sectional panel survey rounds every 2 months.¹⁶ In each round, they recruited a sample of around 1000 participants aged 18 years or older from a panel. The sample was representative of the Spanish general population in terms of sex, age, education, and area of residence. The research company e-mailed to these panel members an invitation to answer an online questionnaire. Methodological aspects have been previously published.^16–18

FIGURE 1—

Epidemic Curve of the Pandemic in Spain With the Dates of the Different Rounds Carried Out From September 2020 to May 2021

Source. Data were obtained from individualized data notified to RENAVE (National Epidemiological Surveillance Network in Spain).

The first-round survey was conducted between September 22 and 25, 2020, during the second wave, when the new school year had already started and schools reopened, and the measures adopted to restrict activity and mobility in different cities and autonomous communities were in place. The cumulative incidence (cases per 100 000 inhabitants) during the previous 2 weeks was 282.29.¹⁹

The second round was conducted between November 24 and 27, 2020, at the end of the second wave in Spain, with mobility restrictions and capacity limitations in commercial establishments still present. At the time, the cases detected reached a cumulative incidence of 307.30 for the last 14 days.¹⁹

Vaccination started on December 27 in Spain. The study third round was held 1 month later, from January 25 to February 1, 2021. The cases detected during the previous 14 days reached a cumulative incidence of 783.25.¹⁹ Mobility restrictions, opening hours of bars and restaurants, and capacity limitations in commercial establishments in different autonomous communities were maintained. A total of 2.64% of the population had received at least 1 vaccination dose, and 0.75% had the full regimen of 2 doses.⁴

The fourth study round was conducted from March 22 to 26, 2021, just before the Easter holidays. The cases detected during the previous 14 days reached a cumulative incidence of 138.63.¹⁹ There were mobility restrictions and time and capacity limitations in commercial establishments in different autonomous communities. A total of 9.62% of the population had received at least 1 vaccination dose, and 5.28% had the full 2-dose regimen.⁴

The last study round was conducted from May 24 to June 3, 2021. The cumulative incidence during the previous 14 days was 198.60 cases.¹⁹ About 39.46% of the Spanish population had at least 1 dose of the COVID-19 vaccine, and 21.04% had 2 doses.⁴

Variables

The online questionnaire collected information on basic sociodemographic data (e.g., sex, age, education level, job status, household members), COVID-19 self-reported infection status, and family members or relatives infected by and deceased from COVID-19. The variables have been described in previous publications.¹⁸

We measured vaccine intention with the question, “If you were offered vaccination against COVID-19 tomorrow, would you get vaccinated?” Answers were rated from 1 (“I would not get the vaccine”) to 5 (“I would get the vaccine for sure”).

Data and Statistical Analysis

We conducted a descriptive analysis of participants’ characteristics and included variables. We described categorical variables with frequency and percentages and continuous variables using median and interquartile range. We recoded the question about vaccination acceptance, considering answers from 1 to 3 as “I disagree with being vaccinated” and 4 and 5 as “I agree with being vaccinated” to assess COVID-19 vaccination acceptance‒related factors. People who had already received a vaccine were recorded as agreeing with being vaccinated. The bivariate analysis using the χ² test can be found in Appendix A (available as a supplement to the online version of this article at https://ajph.org). We included independent variables that were significantly associated with COVID-19 vaccine acceptance at a P value of less than .05 in the multivariable analysis.

We performed a multivariable logistic regression analysis using a backward stepwise procedure to assess factors associated with vaccination acceptance. We computed the odds ratios (ORs) and 95% confidence intervals (CIs), and considered P values of less than .05 to be statistically significant.

We performed time-based trend analysis to measure the effect of the independent variables on the probability of agreement with being vaccinated changing over time. For this purpose, we performed interactions between time and each of the independent variables obtained in the final logistic regression model. We analyzed the significant interactions through margin plots. We used Stata version 15 (StataCorp LP, College Station, TX) to perform all statistical analyses.

RESULTS

Out of 5080 adults included in this analysis, 3156 (62.1%) agreed to be vaccinated against COVID-19 (Table 1). More than half of people who agreed to be vaccinated were men (53.4%), with a median age of 48 (interquartile range = 23) years, were working (54%), and 62.4% had family members or relatives infected by COVID-19, with an increasing trend in vaccination acceptance from September 2020 (43.1%) to May 2021 (84.5%).

TABLE 1—

Participants’ Sociodemographic Characteristics by Vaccination Acceptance and Agreement: Spain, September 2020‒May 2021

Variables	No. (%) or Median (IQR)			OR (95% CI)
Total	Agree	Disagree
Total	5080 (100)	3156 (62.1)	1924 (37.9)
Rounds
Sep 2020	1057 (20.8)	456 (43.1)	601 (56.9)	1 (Ref)
Nov 2020	1018 (20.0)	394 (38.7)	624 (61.3)	0.83 (0.70, 0.99)
Jan 2021	1002 (19.7)	722 (72.1)	280 (27.9)	3.40 (2.83, 4.09)
Mar 2021	1002 (19.7)	738 (73.7)	264 (26.3)	3.68 (3.06, 4.44)
May 2021	1001 (19.7)	846 (84.5)	155 (15.1)	7.19 (5.83, 8.88)
Sex
Men	2534 (49.9)	1685 (53.4)	849 (44.1)	1 (Ref)
Women	2546 (50.1)	1471 (46.6)	1075 (55.9)	0.69 (0.62, 0.77)
Age, y	46 (22)	48 (23)	43 (21)	1.02 (1.02, 1.03)
Education level
Primary studies (aged up to 10 or 11 y)	503 (9.9)	1430 (45.3)	824 (42.8)	1 (Ref)
Secondary studies and above	4577 (90.1)	1726 (54.7)	1100 (57.2)	0.90 (0.81, 1.01)
Job status
Not working	2826 (55.6)	1430 (45.3)	824 (42.8)	1 (Ref)
Working	2254 (44.4)	1726 (54.7)	1100 (57.2)	0.90 (0.81, 1.01)
Household members
Living with another person aged 0‒13 y	1524 (30.0)	876 (27.8)	648 (33.7)	0.76 (0.67, 0.86)
Living with another person aged 14‒60 y	4496 (88.5)	2700 (85.6)	1796 (93.3)	0.42 (0.34, 0.52)
Living with another person aged > 60 y	1740 (34.3)	1190 (37.7)	550 (28.6)	1.51 (1.34, 1.71)
Respondents’ self-reported COVID-19‒infection status
No	4675 (92.0)	2895 (91.7)	1780 (92.5)	1 (Ref)
Yes	405 (8.0)	261 (8.3)	144 (7.5)	0.90 (0.73, 1.11)
Family members or relatives infected by COVID-19
No	2088 (41.1)	1188 (37.6)	900 (46.8)	1 (Ref)
Yes	2992 (58.9)	1968 (62.4)	1024 (53.2)	0.69 (0.61, 0.77)
Family members or relatives deceased from COVID-19
No	2079 (69.5)	1360 (69.1)	719 (70.2)	0.95 (0.81, 1.12)
Yes	913 (30.5)	608 (30.9)	305 (29.8)	1 (Ref)

Note. CI = confidence interval; IQR = interquartile range; OR = odds ratio.

Factors Associated With Vaccine Acceptance

According to the multivariable logistic regression analysis (Appendix B, available as a supplement to the online version of this article at https://ajph.org), vaccine acceptance increased from November 2020 (OR = 0.78) to May 2021 (OR = 13.14; 95% CI = 10.25, 16.84; P < .001). Among the sociodemographic characteristics, women were less likely to be vaccinated (OR = 0.63; P < .001), while acceptance increased with age (OR = 1.01; P < .001). Other factors associated with disagreement with vaccination were a high perceived probability of infection when going to a health center (OR = 0.62; P < .001), being worried about not being able to pay their bills (OR = 0.82), and having a low self-efficacy (OR = 0.81).

Being concerned about COVID-19 (OR = 1.29) and people not wearing a face mask (OR = 1.31) were associated with vaccine acceptance. Adherence to preventive behaviors such as using hydroalcoholic gel and other hand disinfectants (OR = 1.32) and using face masks following national recommendations (OR = 1.75; P < .001), as well as having a high confidence in scientists (OR = 1.72; P < .001) and schools to address the challenges of the COVID-19 pandemic (OR = 1.36; P < .001), were also associated with vaccine acceptance.

Time-Based Trends in Vaccine Acceptance

Respondents worried about people not wearing a face mask agreed with being vaccinated to a much larger extent in March 2021 (OR = 2.1; 95% CI = 1.4, 3.1; P < .001) and in May 2021 (OR = 2.0; 95% CI = 1.3, 3.1; P = .002). We observed the same time trend in people who normally used a face mask in March 2021 (OR = 2.7; 95% CI = 1.5, 4.7; P = .001) and May 2021 (OR = 3.7; 95% CI = 2.1, 6.6; P < .001) or used hydroalcoholic gel in May 2021 (OR = 2.4; 95% CI = 1.5, 3.7; P < .001), and in those who considered it very easy to find information about coronavirus (March 2021: OR = 2.0; 95% CI = 1.4, 2.7; P < .001 and May 2021: OR = 1.9; 95% CI = 1.3, 2.8; P < .001). Similarly, people who were more confident in scientists agreed with vaccination to a much larger extent in January 2021 (OR = 2.0; 95% CI = 1.4, 2.7; P < .001), March 2021 (OR = 1.9; 95% CI = 1.4, 2.7; P < .001), and May 2021 (OR = 2.5; 95% CI = 1.7, 3.8; P < .001), while respondents who were worried about paying their bills had less agreement to be vaccinated in January 2021 (OR = 0.61; 95% CI = 0.5, 0.8; P = .002; Figure 2).

FIGURE 2—

Time-Based Trend Differences in Agreement With Being Vaccinated Against COVID-19 and (a) Use of Masks, (b) Finding Information About COVID-19, (c) Confidence in Scientists, and (d) Concern About Not Being Able to Pay Bills: Spain, September 2020‒May 2021

Note. Adjusted predictions from multivariable logistic regression with interaction between concerns and perceived disease severity about COVID-19, preventive behaviors, health literacy, and confidence in scientists over time during the study period.

DISCUSSION

Vaccination acceptance increased in Spain from September 2020 to May 2021. Understanding vaccine acceptance factors is crucial, even in contexts with high COVID-19 vaccination rates.⁴ In this study, factors such as being male, older age, better health literacy, high pandemic concern, and high risk perception, as well as high adherence to preventive measures and confidence in scientists and institutions, were associated with greater vaccination acceptance.

Being a woman was associated with less agreement to be vaccinated in Spain, as has been found in other studies.²⁰ Vaccination acceptance could have been negatively affected in younger women by rumors regarding COVID-19 vaccines and menstrual cycle problems, infertility, and pregnancy and breastfeeding concerns that had circulated widely on diverse social media.²¹ Concerns about adverse events such as venous thromboembolism or thrombocytopenia may have also influenced their vaccine hesitancy.²² Women’s higher caregiving burden might have played a role, too.

Age was also associated with increasing vaccination acceptance. Older adults agreed with being vaccinated as they are at higher risk of developing a severe disease and dying from potential complications of COVID-19.²³ Different concerns have been associated with vaccination acceptance. Having high perceived risk of infection in home gatherings with friends or family, high-perceived severity if infected, and high concern about unmasked people were factors associated with higher vaccination acceptance in Spain. Worries about the pandemic were also associated with higher vaccination intention in many other countries.^20,24

Regarding the factors associated with disagreeing with vaccination, people very worried about paying their bills were less likely to accept vaccination. Although COVID-19 vaccine was provided free of charge, adults who found it hard to pay their bills were less likely to be vaccinated, possibly because of their low socioeconomic status, fearing side effects that could impair their income-earning capabilities, and other structural barriers such as access to vaccination facilities and opening schedules.^23,25 Other factors related with vaccination disagreement in Spain were having high perception of contagion in health centers and a low self-efficacy. Trust in the vaccines has shown to be critically dependent on governments’ ability to explain the benefits of vaccination and to deliver the vaccines safely and effectively.²⁶

People who always used face masks and cleaned their hands frequently showed a higher level of vaccination acceptance. The association between adherence to preventive measures and acceptance to be vaccinated has been found in other countries.²⁴ In Spain, this association may be related to the population’s willingness to follow all disease prevention‒related recommendations.¹⁷ However, some studies have shown a decreasing agreement to accept COVID-19 vaccine in participants who regarded their good use of masks and other preventive attitudes as substitutes for COVID-19 vaccination.²⁷

Respondents who had higher health literacy and who often looked for COVID-19 information also showed higher vaccination acceptance. Providing health education and tailoring messages to the community’s needs are of capital importance to fight this pandemic. In the Spanish population, a greater COVID-19 vaccination awareness has contributed to increased vaccination rates.²⁸ Health literacy plays a key role in understanding and applying the information provided by governments and health authorities about available COVID-19 vaccines. Promoting acceptance of a vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) essentially involves increasing individuals’ ability to detect fake news, improving their health literacy through education, and consistent vaccine communication strategies by institutions.²⁹

Gathering information from reliable sources such as WHO was associated with higher COVID-19 vaccine acceptance.²⁴ Confidence in the national press has been also associated with vaccination acceptance, as has been seen in other studies, where knowing the latest COVID-19 vaccine news implied more willingness to receive it.³⁰ Given that misinformation has been associated with lower acceptability of COVID‐19 vaccination,²⁶ receiving adequate information on disease risks and vaccination benefits is very important.

Moreover, higher confidence in scientists increased vaccination acceptance in Spain. In contrast to other countries,³¹ the relevance of science for the Spanish population increased during the pandemic because most of the population believed that people should follow scientific advice to contain the virus and considered science to be very important for society.¹³ Confidence in health care professionals’ recommendations was also higher in Spain than in the rest of the European Union,²⁴ another key factor and top facilitator of vaccine acceptance in Spain. This confidence, together with a universal public health system, have been some of the reasons why Spain has a high acceptance of COVID-19 vaccination. This may also be influenced by the recognized efforts made by the Spanish public health system and health professionals responding to the different waves of the pandemic with dedication and commitment.¹³

Furthermore, people who indicated a higher confidence in institutions such as schools addressing the challenges created by COVID-19 pandemic also showed more vaccine acceptance. Unlike the rest of Europe, Spain chose to keep schools open throughout the pandemic with strict protocols, and become one of the Organisation for Economic Co-operation and Development nations where students have missed the fewest days of in-place class learning and with a low number of coronavirus cases during the studied period.³²

People’s agreement with being vaccinated followed an increasing trend from September 2020 to May 2021, with a drop only being noticed in November 2020, just before vaccination started, when hoaxes and conspiracy theories on social networks increased in Spain and were echoed by some mass media.³³ After COVID-19 vaccination started in December 2020, the acceptance rate increased considerably. Spain was suffering its third COVID-19 wave, and the highest number of cases until then was registered in January 2021.¹⁹ As COVID-19 vaccination advanced, vaccination acceptance kept increasing.

People showed an increasing COVID-19 vaccination acceptance in March and May, always after a wave and just before Easter and the summer holidays. Awareness about the importance of being vaccinated seems to grow after a wave and before the holidays, as vaccines could be seen as a way to ensure it is safer to travel and meet family and friends. Moreover, respondents worried about unmasked people also followed this time trend, especially in May when the mass media started to debate face mask usage outdoors and the government finally lifted the compulsory use of face masks outdoors at the end of June 2021.³³

Limitations

This study has several limitations. This was a cross-sectional study, and the results may not be generalizable. Despite being representative at national level, the sample size prevents any assessment of regional differences, and surveys of this type are successive snapshots, each taken at a point in time. Our surveys were conducted in the context of a highly dynamic and changing situation over the pandemic, with daily variations in risk perception and COVID-19 vaccine development itself. Further research is needed to explore in depth the reasons for vaccine hesitancy.

Conclusions

In a changing situation, understanding factors and time trends associated with vaccine acceptance would be helpful to design intervention measures necessary to raise awareness about vaccination’s benefits. Findings from this study highlight how older people who comply with preventive measures, with high risk perception and better health literacy, and who have greater confidence in scientists and institutions have the greatest acceptance of vaccination for COVID-19.

Collaborative communication between science and society about COVID-19 becomes essential. Information campaigns should be targeted at people who have less vaccination acceptance such as women, youths, people with economic problems, and people with low self-efficacy liable to be influenced by fake news, making it easier for them to access evidence-based information. Increasing trust in institutions and health care workers may be key to addressing future pandemics.