Who will accept a COVID-19 vaccine?

Successful global vaccination efforts depend on public vaccine acceptance, but current levels of willingness—both in the United States and globally—are below those needed to achieve community, or herd, immunity for COVID-19. Vaccine hesitancy—a delay in acceptance or refusal of vaccination despite availability—could undermine vaccination efforts and delay global control of the disease.

Three studies this week examine the likelihood of vaccine acceptance in US and global populations, finding high levels of vaccine hesitancy, demographic and geographic variation, and highlighting the importance of clear, credible, culturally-specific vaccine communication.

US vaccine willingness tied to efficacy, other factors

A JAMA Network Open study yesterday is among the first to systematically analyze factors that impact vaccine choice in the United States, finding that higher vaccine efficacy, longer duration of immunity, and lower rates of adverse effects all increase the likelihood of vaccine willingness.

The Jul 9 survey of 1,971 demographically-representative US adults asked participants to evaluate five sets of two hypothetical vaccines, indicating their choice of one or neither vaccine based on attributes such as efficacy, protection duration, major adverse effects, minor adverse effects, US Food and Drug Administration (FDA) approval process, national origin of vaccine, and political figure endorsement.

The most important attribute for vaccine choice was efficacy, with only 51% of participants indicating that they would receive a vaccine with 50% efficacy (95% confidence interval [CI], 0.50 to 0.53). Vaccine acceptance rose to 61% for vaccines showing 90% efficacy, still far below the 70% estimate of coverage needed to provide herd immunity (95% CI, 0.59 to 0.62).

"Our results suggest that 50% efficacy will lead to significant vaccine hesitancy," said co-author Douglas Kriner, PhD, in a Cornell University news release. "We might not get enough people to take it at that level, even though it would be a valuable public health intervention," Kriner said.

An increase in the duration of protective immunity and a reduction in the incidence of major adverse effects were associated with more modest increases in vaccine acceptance—a 2-percentage-point increase for 5-year duration versus 1-year, and a 4-percentage-point increase when adverse effects decreased from 1 in 10,000 to 1 in 1,000,000.

To measure the association between trust in political leaders and institutions and the likelihood of willingness to receive a vaccine, the researchers evaluated a number of political vaccine attributes—full (FDA) approval of the vaccine versus emergency use authorization (EUA), country of vaccine origin, and endorsement by agency or political leaders. Vaccine choice was lower for EUA vaccines (55%) compared to full FDA approval (EUA 54%, 95% CI, 0.53 to 0.57; FDA 57%, 95% CI, 0.56 to 0.59).  

In a commentary in the same journal, the authors recommend that, "If an EUA is indeed used to speed access to COVID-19 vaccines, strategies will be needed to mitigate its potential negative association with vaccine acceptance. At a minimum, the safety and efficacy data informing an EUA decision should be shared with relevant federal vaccine advisory committees. More broadly, the EUA process should be made fully transparent to the public to strengthen confidence in its outcome."

Vaccines originating in China were associated with a 10-percentage-point lower willingness to receive (China 50%, 95% CI, 0.48 to 0.52; US 60%, 95% CI, 0.59 to 0.62). Endorsements by health agencies such as the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) carried more weight with respondents than those from either President Trump or former Vice President Biden (CDC 59%, 95% CI, 0.57 to 0.61; WHO 58%, 95% CI, 0.56 to 0.60; Trump 52%. 95% CI, 0.50 to 0.54; Biden 55%, 95% CI, 0.53 to 0.57).

The authors also identified demographic factors that contribute to vaccine acceptance, finding that older people, black individuals, and women are less likely to receive a vaccine. Because vaccine choice is influenced by political attributes and demographic factors, the authors suggest that public outreach campaigns should prioritize advice from trusted agencies over political figures, and develop messaging targeted to specific groups.

"National and international public health agencies must prioritize facilitating a broad understanding among the public of these processes through frequent, consistent, and visible communication, including engaging with representatives from communities and populations who are disproportionally affected by the pandemic to leverage their knowledge, skills, and expertise and to listen to their concerns. To steer us out of the worst pandemic seen in a century, we see no other way," the commentary authors wrote.

Fewer Americans say they will get vaccine

A survey released this week from STAT and the Harris Poll shows a dramatic decrease since late summer in Americans who say they are likely to get a COVID-19 vaccine as soon as one becomes available, with the decline even more pronounced among black Americans.

The Oct 7 to Oct 10 online, representative survey of 2,050 people asked participants whether they would pursue a vaccine as soon as it became available, as well as whether the news that President Trump tested positive for the coronavirus affected their likelihood to wear masks, physical (social) distance, and receive a vaccine. Responses were compared with baseline values from a similar poll in mid-August.

Poll results reveal that 58% of the general public said they would receive a vaccine versus 69% in mid-August. The disparities are more pronounced when broken down by race, with 59% of white individuals declaring willingness to receive a vaccine (70% in mid-August) and only 43% of black individuals (65% in mid-August).

About 40% of Americans said they are somewhat or much more likely to get the coronavirus vaccine once it is available after the news of President Trump's positive test result, similar among both Republicans and Democrats (41% and 44%, respectively). But mask wearing and physical distancing showed disparities that aligned with political affiliation, with fewer Republicans reporting the likelihood of wearing a mask and practicing physical distancing than Democrats (55% vs 66%, and 51% vs 64%, respectively).

Just 7% of participants said they were somewhat or less likely to practice physical distancing or mask wearing after learning that Trump had developed COVID-19.

The authors point to healthcare disparities and distrust as factors that contribute to racial differences in vaccine acceptance, noting that black people have 2.5 times higher COVID-19 death rates and 5 times higher age-adjusted hospitalization rates. Majority black and Hispanic communities can also expect more crowded testing sites, longer wait times, and increased travel time to testing sites, perhaps contributing to distrust in the healthcare system during the pandemic, the study authors suggest.

"When we're looking at the intersection of vaccine and politics, everything is exaggerated. It's not just racial disparities, but health disparities," said Rob Jekielek, managing director of The Harris Poll. "There's a historical level of distrust, and when you think about stalling the spread of Covid-19, these findings indicate that we face an increasingly bigger problem," Jekielek said.

Global vaccine hesitancy

An international study in Nature Medicine reported yesterday that most people are likely to accept a safe, effective vaccine, but vaccine hesitancy and misinformation could compromise efforts to achieve community immunity.

The survey of 13,426 people in 19 countries—representing 55% of the world population— aimed to gauge public vaccine willingness in order to guide policy decisions, government messaging, and maximize vaccine initiative success. Participants were asked whether they would take a "proven, safe, and effective vaccine," and whether they would accept such a vaccine if it was recommended by their employer.

Overall, the poll results showed that 71.5% of participants would be likely to take a vaccine with 14% refusing and 14% saying they would hesitate, leaving potentially tens of millions unvaccinated worldwide.

The researchers found wide regional variation in acceptance rates ranging from 88.6% in China to 54.9% in Russia. Trust in government—high in Asian nations—was associated with higher odds of accepting a vaccine (odds ratio [OR], 1.67, 95% CI, 1.54 to 1.80), and a greater likelihood of accepting an employer-recommended vaccine (OR, 2.34, 95% CI, 2.20 to 2.56). The overall likelihood of accepting an employer-recommended vaccine across all countries was 61.4%.

Men were less inclined to take a vaccine than women (OR, 0.84, 95% CI, 0.78 to 0.91), and individuals older than 24 were more receptive to vaccines than individuals ages 18 to 24, with the greatest disparity between the oldest (65+) and youngest (18-24) age cohorts (OR, 1.73, 96% CI, 1.48 to 2.02). Higher income and educational level, and higher country case and mortality rates were all associated with a higher likelihood of willingness to take a vaccine.

The percentage of people in all countries who are hesitant or would refuse to take a vaccine could delay global COVID-19 control and compromise economic recovery, the authors wrote.

"It will be tragic if we develop safe and effective vaccines and people refuse to take them. We need to develop a robust and sustained effort to address vaccine hesitancy and rebuild public confidence in the personal, family and community benefits of immunizations," co-author Scott C. Ratzan, MD, MPA, of City University of New York (CUNY) School of Public Health warned in a CUNY news release.

"Our findings are consistent with recent surveys in the US, which show diminished public trust in a COVID-19 vaccine," he concludes.

The study authors also contend that cultural differences in vaccine receptivity require culturally informed, community-specific messaging targeted to local groups. Co-author Heidi J. Larson, PhD, director of the Vaccine Confidence Project said in the release, "These findings should be a call to action for the international health community. If we do not start building vaccine literacy and restoring public trust in science today, we cannot hope to contain this pandemic."

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