Abstract
COVID-19 vaccine hesitancy and suboptimal vaccine uptake rates are pressing public health challenges. Vaccine hesitancy has been observed for different vaccines. For COVID-19 vaccines, multiple factors influence vaccine uptake in the U.S., including political ideology. A more nuanced understanding of the factors influencing COVID-19 vaccine uptake within political parties is needed. This study assesses the relationship between known vaccine hesitancy factors and vaccine uptake within two major political parties. Data from 804 U.S. participants in an online survey from June 2021 was used to assess the association between COVID-19 vaccine uptake (no dose vs. any dose) and categories of factors thought to influence vaccine uptake (sociodemographic variables, COVID-19 disease and vaccine belief variables, belief in COVID-19 prevention behavior variables, and social network features variables) for Republicans and Democrats using bivariate and multivariate regression. 65.4% of the sample reported having received at least one dose of the COVID-19 vaccine (22.6% Republican and 52.1% Democrat). In the total sample bivariate model, Democrat participants had significantly greater odds of having received a dose of the vaccine as compared to Republican participants (OR=2.51, 95%CI=1.73-3.64). In adjusted models, the speed of vaccine development was negatively associated with vaccine uptake for both Republicans (aOR=0.18, 95%CI=0.06-0.57) and Democrats (aOR=0.40, 95%CI=0.19-0.86), as was concern about side effects from the vaccine (Republicans: aOR=0.15; 95%CI=0.05-0.47; Democrats: aOR= 0.14, 95%CI=0.06-0.31). COVID-19 vaccine uptake among Republicans, but not Democrats, was associated with belief that the vaccine prevents COVID-19 (aOR=3.29, 95%CI=1.29-8.37) and belief about friends’ vaccine intentions (aOR=6.19, 95%CI=2.39-16.05). There were no significant factors unique to Democrats. Concerns about aspects of COVID-19 vaccine safety for both political groups suggest that vaccine advocacy interventions should universally address these factors. However, Republican beliefs in vaccine efficacy and in friends’ vaccine intentions suggest a need for Republican-specific messaging.
Keywords: political party, politics, COVID-19, vaccine uptake, vaccine hesitancy, beliefs, social norms, prevention behaviors
Introduction
Suboptimal vaccination rates years into the COVID-19 pandemic in the United States continue to demonstrate major vaccine hesitancy problems in the country. The World Health Organization (WHO) defines vaccine hesitancy as “the reluctance or refusal to vaccinate despite the availability of vaccines” (“Ten Threats to Global Health,” 2022). In March 2021, President Biden announced that 90% of American adults were eligible for vaccination and lived within five miles of a vaccination site (“Remarks by President Biden,” 2021). However, as of November 2022, only 68.6% of eligible Americans completed the primary two dose vaccine series (“COVID Data Tracker,” 2022). Despite overwhelming evidence supporting the efficacy, safety, and necessity of COVID-19 vaccines, over 25% of Americans remain unvaccinated nearly two years after vaccinations became available (“COVID Data Tracker,” 2022). There are three highly effective COVID-19 vaccines available to Americans: the double dose Pfizer-BioNTech and Moderna vaccines and the single dose Johnson and Johnson’s Janssen vaccine. All three have proven to be over 70% effective in preventing hospitalizations due to COVID-19, with the Pfizer and Moderna vaccines reaching 88% and 93% efficacy, respectively (Self et al., 2021). Although side effects can occur, the majority of individuals report only mild to moderate temporary effects (Polack et al., 2020). One study found that while 64.9-80.3% of surveyed individuals reported mild symptoms, severe side effects, like allergic reactions, were quite rare, occurring in 0.2-0.3% of the sample (Beatty et al., 2021). Although the vaccines are effective and safe, American vaccine uptake continues to be problematic.
Vaccine hesitancy is not a new phenomenon, nor is it unique to COVID-19 vaccines. Similar to COVID-19, the flu is a respiratory infection spread through the air (Pleschka, 2012) and like COVID-19 vaccines, the flu vaccine prevents severe illness in breakthrough infections (Ferdinands et al., 2021). The 2009 U.S. H1N1 flu epidemic also raised vaccine hesitancy questions. Higher flu vaccine uptake during H1N1 was associated with Democratic party affiliation, high perceived infection risk, trust in government and healthcare system, and age ≥ 65 (Mesch et al., 2015). In non-outbreak times, one cross-sectional study found that Americans with high vaccine hesitancy had decreased flu vaccine uptake in the past five years. However, confidence in the vaccine and convenience of receiving the vaccine were associated with increased vaccine trust and uptake (Quinn et al., 2019). Schmid et al. found that vaccine safety, risk of disease from the vaccine, social benefit of vaccination, past vaccination behavior, experience with having the flu, and knowledge about the virus and how its vaccine works were associated with flu vaccine hesitancy (Schmid et al., 2017). From the literature on COVID-19 vaccine attitudes, the following categories of factors affect COVID-19 vaccine uptake:
Sociodemographics
Women and Non-Hispanic Black individuals have lower trust in hypothetical COVID-19 vaccines (a vaccine not yet available) (Latkin et al., 2021a) and are less willing to receive a hypothetical COVID-19 vaccine (Kreps et al., 2020). Age was not found to significantly affect COVID-19 vaccine intentions in some studies (Latkin et al., 2021b), but was associated with decreased willingness to receive a vaccine in others (Kreps et al., 2020). Higher education level increased the likelihood of receiving a vaccine (Kreps et al., 2020) and lower income was associated with greater vaccine hesitancy in some studies (Willis et al., 2021).
Beliefs about COVID-19 disease and vaccine
Concerns about vaccine safety, including rapid vaccine development, are common (Pogue et al., 2020) and individuals with these concerns are more likely to have lower COVID-19 vaccine intentions (Chu & Liu, 2021). COVID-19 vaccine side effects are also cited as a fear among Americans (Pogue et al., 2020), as with other vaccines like the flu (Schmid et al., 2017). Beliefs about the legitimacy of COVID-19 also affect the vaccine uptake; for example, people with poor ability to detect fake COVID-19 news are more likely to be hesitant or anti-vaccine (Montagni et al., 2021).
Beliefs in COVID-19 prevention variables
Engaging in COVID-19 prevention behaviors like social distancing and mask wearing increase vaccine intentions (Latkin et al., 2021b). Additionally, concerns about vaccine efficacy affect vaccine attitudes. One study found that a hypothetical COVID-19 vaccine efficacy rate of 99% increased vaccine intentions as compared to efficacies of 50% or 75% (Pogue et al., 2020).
Social Network Features
Vaccination attitudes within social networks can affect individual members’ beliefs. Perceptions of vaccine hesitancy within a group can influence individuals’ vaccine intentions in a network; this has been observed for the flu vaccine (Bruine de Bruin et al., 2019). Similarly, decreased COVID-19 prevention behaviors within an individual’s social network are associated with decreased vaccine intentions (Latkin et al., 2021b).
Political Ideology
Political differences influence COVID-19 vaccine uptake in the U.S. (Kempthorne & Terrizzi, 2021). There is a political divide in responses to COVID-19 with more politically conservative individuals being less likely to trust a COVID-19 vaccine (Latkin et al., 2021a). Voting for the Republican candidate in the 2020 election has a strong negative association with COVID-19 vaccination, and Republicans are less willing to be vaccinated (Agarwal et al., 2021). COVID-19 case and death rates are also higher in politically conservative areas, potentially attributed to acceptance and implementation of public health guidelines (Eden et al., 2021). Thus, it is established that there are differences in COVID-19 vaccine uptake based on political partisanship. Political affiliation is a strong predictor of vaccine uptake (Kempthorne & Terrizzi, 2021; Agarwal et al., 2021; Kreps et al., 2020), which is likely partially attributable to the highly politicalized COVID-19 information communication by public figures since the early pandemic (Hart et al., 2020).
However, political parties in the U.S. are composed of diverse groups of people with different motivations and intentions (Pew Research Center, 2016) and less is known about the nuances of why this relationship exists and what factors influence vaccine uptake within specific political parties. One study identified differences in risk perception by political party, with Republicans more likely to perceive lower individual and public risk from COVID-19 compared to Democrats (Kiviniemi et al., 2022). However, numerous variables affect COVID-19 vaccine intentions or uptake, which may have differential party effects. Given the limited research on why these differences exist, we analyzed the associations of sociodemographics, beliefs about COVID-19 disease and vaccines, beliefs in COVID-19 prevention behaviors, and social network features with COVID-19 vaccine uptake within U.S. Republicans and Democrats. Investigating the relationship between each factor and COVID-19 vaccine uptake within political parties offers a more nuanced understanding of what influences the vaccine decision making within each group.
Materials and Methods
This cross-sectional study used participants from a large ongoing online longitudinal COVID-19 and Well-Being study (Latkin et al., 2021a; Latkin et al., 2021b; Latkin et al., 2022). Starting in March 2020, participants were recruited through Amazon Mechanical Turk (MTurk), an online platform through which members, known as “workers,” complete “Human Intelligence Tasks” (HITs), including research surveys (Amazon Mechanical Turk, 2018). Validity and attention checks were included throughout the survey. MTurk is frequently used to quickly obtain large, diverse data samples (Créquit et al., 2018). Although workers are often younger and more liberal than the general population (Berinsky, 2012), MTurk produces reliable information (Follmer et al., 2017) and higher quality data (Chandler & Shapiro, 2016) that is more representative compared to other sampling programs (Huff & Tingley, 2015). The study eligibility criteria were the following: MTurk user ages ≥18, living in the U.S., able to speak and read English, had heard of COVID-19, and consented to participate.
Data from the sixth survey was used to for the present analysis as COVID-19 vaccines were widely available at this time. This survey was conducted in June 2021, after Pfizer-BioNTech, Moderna, and Johnson & Johnson’s Janssen vaccines become available to adults ages 18 and older. At this time, the Pfizer vaccine was also approved for children ages 12 to 17 (“Coronavirus (COVID-19) Update,” 2021). By summer 2021, the Centers for Disease Control and Prevention (CDC) published a study demonstrating that the Pfizer and Moderna vaccines reduced COVID-19 infection risk by 91% (“CDC COVID-19 Study,” 2021). The CDC also recommended that Americans wear masks indoors, although outdoor masks guidelines were relaxed (“Order: Wearing of face masks,” 2021). We conducted additional recruitment to increase racial, economic, and political diversity in the sample. Four eligible participants with missing responses were excluded, resulting in 804 participants included in the current study. Participants were paid $4.25 for completing the survey. The study was approved by the Johns Hopkins Bloomberg School of Public Health IRB.
Measures
Sociodemographic Variables
We included questions about age, sex, race, education level, income level, and political affiliation. Age was assessed as a continuous variable. Race included White, Non-Hispanic Black, Hispanic, Asian, Mixed, and other. Asian, Mixed, and other were collapsed into an “other” category due to small sample sizes. Education and income level variables were dichotomized using the mean. Political party (Republican, Democrat, Other) was included as a categorical variable in analysis of the total sample.
COVID-19 Disease and Vaccine Belief Variables
All survey questions included in the study used the term, “coronavirus,” which refers to the virus that causes COVID-19 disease. We assessed these beliefs using the questions, “I am concerned that the coronavirus vaccines are being developed too quickly,” “I am worried about bad side effects if I got a coronavirus vaccine,” and “The coronavirus is a hoax.” Each question had response options of “Strongly agree,” “Agree,” “Neither agree nor disagree,” “Disagree,” and “Strongly disagree.” We dichotomized these answers into agree (strongly agree and agree) and disagree (strongly disagree, disagree, neither agree nor disagree).
Belief in COVID-19 Prevention Variables
Participants were asked, “Face masks will help stop the spread of the coronavirus” and “A vaccine will prevent me from getting the coronavirus” with the agreement scale answer choices. Answer choices were dichotomized into agree and disagree.
Social Network Features Variables
To assess participants’ social networks, we used the question, “The majority of my friends will get the coronavirus vaccine, when available” with the agreement scale answer choices, dichotomized into agree and disagree. We created a variable assessing political homogeneity in friendships by subtracting answers to the question, “What percent of your friends are Democrats?” from “What percent of your friends are Republicans?” Answer choices were percentages from 0 to 100% in 10% increments. Negative values indicated a greater percentage of Democrat friends, while positive values corresponded to more Republican friends.
Analyses
Using IBM’s SPSS 27 Statistics software platform (IBM Corp., 2020), we analyzed the relationships between different factors and COVID-19 vaccine uptake. Models were created for the overall population and for Republican and Democrat subgroups. The main outcome variable was vaccination status (no dose vs. any dose). First, bivariate analysis was conducted with the covariates and outcome variable. Then, multivariable models analyzed the relationship between vaccine uptake and each covariate, adjusting for other covariates. Odds ratios were considered significant if p<0.05. Covariates included age, sex at birth, race, education, income, concern about the speed of vaccine development, concern about bad side effects from the vaccine, belief that the COVID-19 is a hoax, belief that face masks help stop the spread of the COVID-19, belief that the vaccine will prevent COVID-19, belief that the majority of one’s friends will get vaccinated, and political homogeneity in friendships. Variables were chosen based on the literature and potential intervention implications.
Results
Table 1 presents descriptive statistics. Out of 804 participants, 65.4% received at least one dose of the COVID-19 vaccine, while 34.6% were unvaccinated. A quarter (25.5%, N=205) identified as Republican, 43.9% as Democrat (N=353), and 30.6% (N=246) as other. Of those reporting any dose, 22.6% were Republicans and 52.1% were Democrats. More participants reported female sex at birth (54.6%) than male (45.4%). The majority of participants were white (65.5%), followed by Non-Hispanic Black race (16.4%), Hispanic (9.2%), and other (8.8%). The mean age of participants was 40.3 years old (SD=12.0). Over half of participants reported earning $60,000 or less per year (55.7%), and less than half of the participants held an Associate’s degree or less (41.3%).
Table 1.
Descriptive statistics, disaggregated by political affiliation and vaccination status
| Descriptive Statistics | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Total (N=804) |
Republicans (N=205) |
Democrats (N=353) |
|||||||
| Total (N=804) |
Any Dose (N=526) |
No Dose (N=278) |
Total (N=205) |
Any Dose (N=119) |
No Dose (N=86) |
Total (N=353) |
Any Dose (N=274) |
No Dose (N=79) |
|
| N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
N (%) or Mean (SD) |
|
| SOCIODEMOGRAPHIC VARIABLES | |||||||||
| Age | 40.3 (12.0) |
41.2 (12.5) |
38.7 (11.0) |
43.8 (12.4) |
45.6 (13.1) |
41.2 (11.0) |
39.0 (11.6) |
39.3 (12.0) |
38.0 (10.2) |
| Race (Ref: White) | |||||||||
| Non-Hispanic Black | 132 (16.4) |
78 (14.8) |
54 (19.4) |
16 (7.8) |
10 (8.4) |
6 (7.0) |
80 (22.7) |
54 (19.7) |
26 (32.9) |
| Hispanic | 74 (9.2) |
51 (9.7) |
23 (8.3) |
15 (7.3) |
10 (8.4) |
5 (5.8) |
41 (11.6) |
35 (12.8) |
6 (7.6) |
| Other | 71 (8.8) |
52 (9.9) |
19 (6.8) |
15 (7.3) |
10 (8.4) |
5 (5.8) |
29
(8.2) |
26 (9.5) |
3 (3.8) |
| Female Sex at birth | 439 (54.6) |
285 (54.2) |
154 (55.4) |
118 (57.6) |
66 (55.5) |
52 (60.5) |
199 (56.4) |
149 (54.4) |
50 (63.3) |
| Household Income Level Below $60K/year |
448
(55.7) |
271 (51.5) |
177 (63.7) |
97 (47.3) |
52 (43.7) |
45 (52.3) |
208
(58.9) |
152 (55.5) |
56 (70.9) |
| Associate’s degree or less |
332
(41.3) |
180 (34.2) |
152 (54.7) |
78
(38.0) |
37 (31.1) |
41 (47.7) |
133
(37.7) |
93 (33.9) |
40 (50.6) |
| Political Affiliation | |||||||||
| Republican | 205 (25.5) |
119 (22.6) |
86 (30.9) |
X | X | X | X | X | X |
| Democrat | 353 (43.9) |
274 (52.1) |
79 (28.4) |
X | X | X | X | X | X |
| Other |
246
(30.6) |
133 (25.3) |
113 (40.6) |
||||||
| COVID-19 DISEASE AND VACCINE BELIEF VARIABLES | |||||||||
| Concern that the vaccines are being developed too quickly |
326
(40.5) |
117 (22.2) |
209 (75.2) |
122
(59.5) |
44 (37.0) |
78 (90.7) |
88
(24.9) |
39 (14.2) |
49 (62.0) |
| Worried about bad side effects from the vaccines |
348
(43.3) |
125 (23.8) |
223 (80.2) |
115
(56.1) |
38 (31.9) |
77 (89.5) |
109
(30.9) |
51 (18.6) |
58 (73.4) |
| Belief that the coronavirus is a hoax |
32
(4.0) |
12 (2.3) |
20 (7.2) |
20
(9.8) |
7 (5.9) |
13 (15.1) |
8 (2.3) |
4 (1.5) |
4 (5.1) |
| BELIEF IN COVID-19 PREVENTION BEHAVIORS VARIABLES | |||||||||
| Belief that face masks will help stop the spread of the coronavirus |
589
(73.3) |
447 (85.0) |
142 (51.1) |
112
(54.6) |
82 (68.9) |
30 (34.9) |
318
(90.1) |
253 (92.3) |
65 (82.3) |
| Belief that vaccines prevent getting the coronavirus |
510
(63.4) |
430 (81.7) |
80 (28.8) |
110
(53.7) |
91 (76.5) |
19 (22.1) |
273
(77.3) |
236 (86.1) |
37 (46.8) |
| SOCIAL NETWORK FEATURES VARIABLES | |||||||||
| Belief that majority of friends will get vaccinated |
553
(68.8) |
446 (84.8) |
107 (38.5) |
125
(61.0) |
98 (82.4) |
27 (31.4) |
279
(79.0) |
237 (86.5) |
42 (53.2) |
| Percent friends Republican or Democrat |
−2.1
(4.6) |
−3.0 (4.4) |
−0.5 (4.5) |
2.1 (3.9) |
1.5 (4.0) |
2.9 (3.5) |
−5.0
(3.5) |
−5.2 (3.3) |
−3.9 (3.8) |
Note: Bolded* indicates statistical significance (p<0.05)
Table 2 shows results from bivariate (Models 1A, 2A, and 3A) and multivariate models (Models 1B, 2B, and 3B). In Model 1A (total sample) bivariate regression, Democrats had 2.51 greater odds of vaccination compared to Republicans (OR=2.51, 95%CI=1.73-3.64). In the multivariate regressions, political affiliation was no longer significant, which was likely due to the other politically influenced variables (like political homogeneity) in this adjusted model.
Table 2.
Bivariate and multivariate data models for COVID-19 vaccination
| Odds Ratios | ||||||
|---|---|---|---|---|---|---|
| Political Affiliation | Model 1 Total Sample (N=804) |
Model 2 Republican Sample (N=205) |
Model 3 Democrat Sample (N=353) |
|||
| Model 1A | Model 1B | Model 2A | Model 2B | Model 3A | Model 3B | |
| OR (95% CI) |
aOR (95% CI) |
OR (95% CI) |
aOR (95% CI) |
OR (95% CI) |
aOR (95% CI) |
|
| SOCIODEMOGRAPHIC VARIABLES | ||||||
| Age | 1.02 (1.01-1.03) * | 1.02 (1.00-1.04) * | 1.02 (1.01-1.03) * | 1.02 (0.98-1.06) | 1.01 (0.99-1.03) | 1.02 (0.99-1.06) |
| Sex assigned at birth | 0.95 (0.71-1.28) | 1.39 (0.91-2.14) | 0.814 (0.46-1.43) | 0.78 (0.31-1.96) | 0.69 (0.41-1.16) | 1.39 (0.69-2.81) |
| Race (Ref: White) | REF | REF | REF | REF | REF | REF |
| Non-Hispanic Black | 0.76 (0.52-1.13) | 1.10 (0.62-1.94) | 1.31 (0.45-3.78) | 0.66 (0.15-2.93) | 0.58 (0.32-1.02) | 1.09 (0.51-2.34) |
| Hispanic | 1.17 (0.69-1.98) | 1.18 (0.56-2.47) | 1.57 (0.51-4.81) | 0.34 (0.06-2.03) | 1.61 (0.64-4.08) | 2.66 (0.80-8.79) |
| Other | 1.44 (0.83-2.52) | 1.30 (0.62-2.74) | 1.57 (0.51-4.81) | 1.20 (0.24-6.07) | 2.40 (0.69-8.30) | 2.63 (0.54-12.92) |
| Household Income Level | 1.65 (1.22-2.22) * | 1.45 (0.93-2.27) | 1.41 (0.81-2.47) | 2.11 (0.75-5.96) | 1.95 (1.14-3.36) * | 1.11 (0.55-2.26) |
| Education Level | 2.32 (1.72-3.12) * | 1.56 (1.01-2.41) * | 2.02 (1.14-3.59) * | 1.07 (0.40-2.86) | 2.00 (1.20-3.31) * | 1.49 *0.75-2.93) |
| Political Affiliation (Ref: Republican) | REF | REF | X | X | X | X |
| Democrat | 2.51 (1.73-3.64) * | 0.81 (0.43-1.53) | X | X | X | X |
| Other | 0.85 (0.59-1.24) | 0.61 (0.34-1.08) | X | X | X | X |
| COVID-19 DISEASE AND VACCINE BELIEF VARIABLES | ||||||
| Concerned the vaccines are being developed too quickly | 0.09 (0.07-0.13) * | 0.46 (0.28-0.75) * | 0.06 (0.03-0.14) * | 0.18 (0.06-0.57) * | 0.10 (0.06-0.18) * | 0.40 (0.19-0.86) * |
| Worried about bad side effects from the vaccines | 0.08 (0.05-0.11) * | 0.19 (0.12-0.32) * | 0.06 (0.03-0.12) * | 0.15 (0.05-0.47) * | 0.08 (0.05-0.15) * | 0.14 (0.06-0.31) * |
| The coronavirus is a hoax | 0.30 (0.15-0.63) * | 0.80 (0.33-1.95) | 0.35 (0.13-0.92) * | 0.96 (0.24-3.86) | 0.28 (0.07-1.14) | 1.51 (0.30-7.66) |
| BELIEFS ABOUT COVID-19 PREVENTION BEHAVIORS VARIABLES | ||||||
| Belief that face masks will help stop the spread of the coronavirus | 5.42 (3.88-7.58) * | 1.97 (1.19-3.26) * | 4.14 (2.30-7.46) * | 2.09 (0.81-5.37) | 2.60 (1.25-5.38) * | 2.11 (0.78-5.72) |
| Belief that vaccines prevent getting the coronavirus | 11.09 (7.88-15.59) * | 3.15 (2.00-4.94) * | 11.46 (5.91-22.23) * | 3.29 (1.29-8.37) * | 7.05 (4.03-12.44) * | 2.09 (0.99-4.40) |
| SOCIAL NETWORK FEATURES VARIABLES | ||||||
| Belief that majority of friends will get vaccinated | 8.91 (6.35-12.51) * | 3.01 (1.91-4.75) * | 10.20 (5.30-19.64) * | 6.19 (2.39-16.05) * | 5.64 (3.22-9.89) * | 1.74 (0.82-3.72) |
| Political homogeneity in friendships | 0.89 (0.86-0.92) * | 0.98 (0.92-1.04) | 0.91 (0.84-0.98) * | 0.95 (0.82-1.10) | 0.90 (0.83-0.96) * | 0.93 (0.85-1.03) |
Note: Bolded* indicates statistical significance (p<0.05)
In Model 1B, age (aOR=1.02, 95%CI=1.00-1.04), education (aOR=1.56, 95%CI=1.01-2.41) and belief in the efficacy of face masks increased odds of vaccination (aOR=1.97, 95%CI=1.19-3.26). Belief that vaccines were developed too quickly and concern about bad vaccine side effects were associated with reduced odds of vaccination in all adjusted models (Model 1B: aOR=0.46, 95%CI=0.28-0.75; Model 2B: aOR=0.18, CI=0.06-0.57; Model 3B: aOR=0.40, CI=0.19-0.86). When looking at differences between political parties, belief that vaccines prevent COVID-19 increased odds of vaccination in Models 1B and 2B only (aOR=3.15, CI=2.00-4.94 and aOR=3.29, CI=1.29-8.37). Additionally, believing that the majority of one’s friends would get vaccinated increased individual odds of vaccination in Models 1B and 2B only (aOR=3.01, CI=1.91-4.75 and aOR=6.19, CI=2.39-16.05). In the adjusted models, income, belief that COVID-19 is a hoax, and political homogeneity did not remain significant.
Discussion
We found both similarities and differences between major U.S. political parties regarding factors affecting COVID-19 vaccine uptake. Similar to previous studies, results showed Democrats were more likely to be vaccinated compared to Republicans. Factors negatively associated with vaccine uptake in both parties were belief that vaccines were developed too quickly and concern about bad side effects. These variables are common among Americans; studies show that COVID-19 vaccine development speed (Pogue et al., 2020; Chu & Liu, 2021) and side effects (Pogue et al., 2020) influence Americans’ vaccine attitudes. Thus, these findings suggest that future vaccination campaigns should address this in a way that is understandable for the general public. This information can be used to mitigate political party divides and to increase vaccine uptake in future pandemics.
Study findings also indicate there are Republican-specific factors influencing vaccine attitudes. Beliefs about COVID-19 prevention behaviors affected vaccine uptake in Republicans but not Democrats. Republicans who believed that vaccines prevent COVID-19 infection had 3.29 higher odds of vaccination compared to Republicans without this belief, suggesting that believing in the efficacy of a vaccine translates into vaccine uptake. One possibility for why this relationship was significant and strong within the Republican sample and not the Democrat sample is that at the beginning of the pandemic, prominent Republican political figures contributed to skepticism about COVID-19 and voiced opinions against the efficacy of hypothetical vaccines and prevention behaviors. In early 2020, President Trump minimized the severity of the pandemic and resisted COVID-19 prevention guidelines (Kerr et al., 2021). This outspoken skepticism about vaccination, which was not seen as much within the Democratic party, could have affected Republican beliefs about the COVID-19 vaccine efficacy. Suggestions for interventions include preventing spread of misinformation and promoting the distribution of vaccine efficacy information; for example, through regulation of misinformation on social media, where false vaccine information spreads and contributes to vaccine hesitancy (Muric et al., 2021).
Additionally, believing the majority of one’s friends will get vaccinated led to 6.19 greater odds of vaccination for Republicans but was not significant in the Democrat sample. Based on these findings, peer diffusion strategies may be useful. Observing peer decision making influences an individual’s own choices, particularly when preferences align between the peers (Yu et al., 2021). Educating individuals about COVID-19 vaccines may spread beneficial information within their social network and based on our results, could increase vaccine uptake, particularly in politically conservative areas.
After adjusting, we did not find any significant factors unique to Democrats. For Democrats, as with Republicans, concern about the speed of vaccine development and concern about vaccine side effects were significant. Not only are these factors salient for both political parties, but they are also the only factors associated with vaccine uptake for Democrats. Although a higher percentage of Democrats received any dose compared to Republicans (Democrats=77.6%, Republican=58.0%; P value= <0.0001), almost a quarter of Democrats remained unvaccinated. This suggests that for Democrats, beliefs have the greatest influence on vaccine uptake; thus, strategies to increase uptake should focus on changing beliefs about the safety of COVID-19 vaccines. Since beliefs were significantly associated with uptake in both parties, these factors are critical to consider when addressing U.S. COVID-19 vaccine uptake in general. Further research should determine if different messaging is needed for each party and if the efficacy of this messaging differs depending on the individual or institution presenting it. Additionally, with the availability of multiple booster shots and the updated vaccination guidelines, further analysis in political differences in factors that affect COVID-19 vaccine uptake should be conducted.
There are several limitations to this study. By dichotomizing the vaccine uptake outcome variable into any dose and no dose, we did not look at nuanced vaccination statuses (such as partial vaccination). Despite the benefits of MTurk as a research platform, the data collected through this program was not nationally representative. Democrats were over-represented in our study population. Additionally, we analyzed only two prominent political groups and did not disaggregate other parties from the total sample (for example, Libertarians) because of small group sample sizes groups. This limits our results to just two parties. Lastly, since analysis was cross-sectional, we could not evaluate cause and effect nor changes in attitudes over time during the rapidly changing pandemic. Consequently, we can only infer correlations between different variables and vaccine uptake with political parties. However, this study has several strengths. Our sample size was large and geographically and politically diverse, and the findings provide valuable information for policy development and interventions to increase COVID-19 vaccine uptake.
In conclusion, this study provides evidence for political party similarities and differences in factors affecting COVID-19 vaccine uptake. This information will continue to be relevant for the current COVID-19 pandemic and will provide lessons learned for future pandemics or outbreak situations.
Acknowledgments
Study participants
Funding
This work was supported by National Institute on Drug Abuse under Grant Number: R01 DA040488 Johns Hopkins Alliance for a Healthier World
Footnotes
Declaration of Interest Statement
No potential conflict of interest was reported by the authors.
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