COVID‐19 Vaccine Booster Hesitancy among Hispanic Adults: The Puerto Rico Community Engagement Alliance (PR‐CEAL) against COVID‐19 Disparities

1. Introduction

From March 2020 through February 14, 2023, 442,788 confirmed cases of COVID-19 and 5,759 deaths were reported in Puerto Rico (PR) [1]​, a US territory primarily composed of Hispanic. Nine months after the promotion of education strategies for the mitigation and prevention of the spread of the virus (December 2020), vaccines became available in PR for a select group of the population; the remainder of the population gained access to the vaccines in early 2021. The primary series vaccination rate of the COVID-19 vaccine in PR was approximately 86.3% ​​[2] and was one of the highest in the United States ​[3]​. However, in terms of booster completion, this extraordinary accomplishment was not duplicated. According to the PR Department of Health (PRDH), only 34.6% of the population have received the booster dose recommended by the Centers for Disease Control and Prevention (CDC) ​[4,1]. Several studies have discovered that booster doses have not been accepted to the same degree that the primary series of the vaccine has ​[5,6,7].​

Vaccine hesitancy is a major public health problem, especially given the magnitude of the COVID-19 pandemic ​[5]. For the Hispanic population, compared with non-Hispanic whites, a high uptake for the primary series and a remarkably lower rate for booster uptake was documented ​[8]. It is of primary concern that Hispanics have lower rates of booster uptake compared to non-Hispanic whites, despite the former’s disproportionate burden of COVID-19 compared to the latter’s as observed during the pandemic ​[8]. In the study of Baker and colleagues, it was documented that Hispanics had higher rates of deaths caused by COVID-19 than did non-Hispanic whites ​​[8].

In addition to the influences of social and environmental factors on booster vaccine uptake, the beliefs and attitudes of the population of interest may also have played a part in the low booster vaccination rate. Multiple studies have documented the unwillingness of some individuals to receive both the COVID-19 vaccine primary series and the booster dose ​​[9,10]. Qin and colleagues revealed that the primary reasons given for refusing the booster vaccine were the complicated vaccination process (e.g., long waiting lines and difficulties obtaining appointments) and uncertainty about the safety and effectiveness of the vaccine ​​[10].

It is important to understand the perceptions and attitudes at the population level to develop efficient strategies to address vaccine hesitancy. To this end, the health belief model (HBM) has been used recently in many studies about vaccinations for COVID-19 and other illnesses, such as influenza ​[9,10,11]​. The HBM is composed of a series of constructs that include perceived susceptibility, perceived severity, perceived benefits, perceived barriers, and cues to action ​[11]. According to the results of Qin and colleagues (2022), those who perceived themselves to have a low susceptibility to COVID-19 were more likely to refuse the booster dose than were their counterparts who perceived themselves as having a greater level of susceptibility ​​[10]. An earlier study by our team showed that the factors perceived susceptibility, vaccination benefits, barriers, and cues to action were associated with the unwillingness of some Puerto Rican adults to receive a COVID-19 vaccine ​[9].​ Based on these findings, we aimed to assess the health-belief correlates of COVID-19 booster uptake, doing so using data collected as part of the PR Community Engagement Alliance (PR-CEAL) initiative.

2. Materials and Methods

2.1. Puerto Rico-Community Engagement Alliance

In the past 2 years, the PR-CEAL has led efforts to address COVID-19 health disparities, misinformation, and mistrust of the vaccination process (including the booster vaccine).

2.2. Study Design

Along with our CEAL partners, nationwide, we have made efforts to develop and implement a single COVID-19 survey that could be used across multiple populations. Among the emerging indicators that informed the design of the survey were general sociodemographic information, social determinants of health, COVID-19 prevention behaviors, testing behaviors, perceived trusted sources of information about COVID-19, and general perceptions of COVID-19. Important sources of data included the results of several clinical trials. The first version of the survey was developed in October 2021. Due to the dynamic nature of the pandemic and since the implementation of the vaccine, a second version of the common survey has been developed (December 2021); this version took into consideration a given respondent’s intention to get a COVID-19 booster vaccine, the prevalence of chronic conditions in that individual, whether he or she had received the influenza vaccine, his or her self-perceived mental health, and that individual’s screening practices for cancer and other common diseases in PR. Using the HBM as reference, our team added several questions to the second version of the CEAL common survey. These questions examined beliefs, behaviors, and the impact of the pandemic on adults residing in Puerto Rico ​[10].​

After the completion of the survey design, in-person participant recruitment started on December 30, 2021, and consisted of visiting supermarkets and community settings on the island. This recruitment initiation date was before the spread of the Omicron variant. After this new variant of COVID-19 was reported in PR, the team adapted a new recruitment strategy that used only online recruitment. The team used different platforms, including Facebook, Instagram, and email blasts directed at academic groups, to invite individuals to complete the online survey. The inclusion criteria for participation in our study were being 18 years old or older, a resident of PR, and able to answer the questionnaire in Spanish.

The Institutional Review Board (IRB) of the University of PR Medical Sciences campus approved the study (IRB protocol number: 6050220). Each participant who finished the survey received a $30 gift card, which was sent via certified mail upon completion of the questionnaire.

2.3. Measurements

2.3.1. Main outcome variables

Booster acceptance was assessed with the question “Do you intend to get a booster shot?” as established in the CEAL common survey. Response options were “I already got the booster,” “I will get it as soon as possible,” “I am going to wait to see how it affects others,” “I have no intention to get the booster soon, but I could sometime in the future,” and “not at all.” All the participants who answered, “I already got the booster” were considered to be accepting of it. The participants who used any other response were considered to be refusing to accept the booster. Beliefs about the COVID-19 booster vaccine were assessed using the HBM constructs defined by Wong, et al. We examined the following 5 constructs: perceived susceptibility (My chance of getting COVID-19 in the next few months is great; I am worried about the likelihood of getting COVID-19; and Getting COVID-19 is currently a possibility for me), perceived severity (Complications from COVID-19 are serious; I will be very sick if I get COVID-19; and I am afraid of getting COVID-19), perceived benefits (A booster dose is a good idea because it makes me feel less worried about catching COVID-19; and Getting the booster will decrease my chance of getting COVID-19 or its complications), perceived barriers (I worry that the possible side effects of the COVID-19 booster vaccine would interfere with my usual activities; I am concerned about the efficacy of the COVID-19 booster vaccine; and I am concerned about the safety of the COVID-19 booster vaccine), and cues to action (I will take the booster only if I am given adequate information about it; and I will take the COVID-19 booster only if the vaccine is taken by many in the public).

The sociodemographic characteristics collected included age, sex, education level, annual income, ethnicity, health insurance, and marital status. The variables that were included here were similar to those of other studies, which had found that they—said variables—influence the thoughts and beliefs of people [9,10]. For the analysis, age, education level, income, and marital status were grouped for convenience. We assessed religiosity with 1 item that asked each respondent about the importance of religion in his or her life, and the answer options ranged from not important to very important.

2.4. Statistical analysis

A chi-square or Fisher’s exact test was used to assess the associations between sociodemographic characteristics, HBM constructs, and booster-vaccine acceptance. Poisson regression models with robust variance were used to estimate the prevalence ratios and 95% confidence intervals (CIs) for each outcome of interest. The models were adjusted based on bivariate analysis significance for income, health insurance, marital status, and the importance of religion. All the statistical analyses were performed using Stata version 17 (StataCorp LLC, College Station, TX, USA).

3. Results

A total of 787 participants were included in this analysis. Table 1 shows the demographic characteristics of the participants. The majority (72.2%) were women, and 71.7% had a college degree or greater. The mean (and standard deviation) age of participants was 38.6 (±14.1) years. The vast majority (96.5%) of the participants self-identified as Puerto Rican, 46.9% were single, and 31.1% indicated that religion was very important for them. In terms of income, 54.5% of participants reported having an annual income lower than $40,000. Regarding COVID-19 booster vaccine outcomes, 78% reported already having gotten the booster, and 22% either had refused the booster or would get it as soon as possible.

Income and having health insurance were statistically significantly associated with booster refusal (p<0.05). Marital status, the importance of religion, and most recent health check achieved marginal significance. In general, almost all the HBM constructs were associated with booster refusal, except for the following: “My chance of getting COVID-19 in the next few months is high,” “Getting COVID-19 is currently a possibility for me,” and “I will be very sick if I get COVID-19”; these all achieved statistical significance in bivariate analysis (p>0.05) (Table 2).

As shown in Table 3, those who were not worried about getting COVID-19 presented a prevalence ratio of 2.24 (95% CI: 1.61, 3.13) for booster refusal, after adjusting for the covariates. Those who did not recognize COVID-19 as a severe illness or who reported being afraid of COVID-19 (perceived severity construct) presented adjusted prevalence ratios of 3.49 (95% CI: 2.41, 5.05) and 1.99 (95% CI: 1.43, 2.76), respectively. In general, the participants who disagreed that getting the booster dose either made them feel less worried about COVID-19 or decreased their chances of getting COVID-19 presented higher booster-refusal prevalence ratios (adjusted prevalence ratio: 4.20, 95% CI: 3.00, 5.90; adjusted prevalence ratio: 3.67, 95% CI: 2.63, 5.14). Similarly, participants who perceived barriers such as being worried about side effects or the efficacy or safety of the booster vaccine presented higher prevalence of booster refusal (adjusted prevalence ratio: 2.41, 95% CI: 1.70, 3.40; adjusted prevalence ratio: 2.47, 95% CI: 1.74, 3.51; adjusted prevalence ratio: 2.71, 95% CI: 1.91, 3.84).

5. Conclusions

Our study found that 22% of participants were unwilling to receive the booster doses of any of the COVID-19 vaccines. Based on the HBM model, and even with our high booster acceptance, the study was able to identify strong predictors of unwillingness. People having low confidence in the vaccine and who perceive that they are at low risk of getting COVID-19 are more likely to refuse the booster. In addition, those participants who perceived higher benefits in relation to the booster dose presented higher acceptance of the vaccine. More and better education is necessary if we are to increase confidence in the COVID-19 booster vaccines.