In a recent study published within the journal Vaccine, researchers investigated why greater than 80% of eligible Americans haven’t taken their severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) vaccine booster dose. They conducted an internet survey of two,298 respondents to judge the explanations underlying the low observed response.

Their results elucidate that, despite consistent research and clinical reports depicting positive, anti-coronavirus disease of 2019 (COVID-19) outcomes for people receiving the booster, misinformation regarding prior SARS-CoV-2 infection and vaccination, and concerns pertaining to vaccine uncomfortable side effects and the presence and degree of protection conferred by the booster stalled booster reception in the USA (US). These results highlight the necessity for extra media outreach elucidating the advantages of COVID-19 vaccines as the perfect intervention against the disease, especially severe infections by SARS-CoV-2.

Study: Understanding low COVID-19 booster uptake amongst US adults. Image Credit: angellodeco / Shutterstock

A background on COVID-19 and vaccination drives

The continuing coronavirus disease of 2019 (COVID-19) pandemic stays one among the worst in recorded history, with the World Health Organization (WHO) COVID-19 dashboard reporting almost 771 million confirmed cases and almost 7 million deaths worldwide. Brought on by the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) virus, COVID-19 has represented one of the vital intensive efforts in vaccine and medicine development efforts ever, with vaccination drives being second only to self-isolation within the itineraries of most governments globally.

Scientific and medical research has unanimously advocated for vaccination as the perfect intervention to effectively decrease COVID-19 disease severity and reduce hospitalizations, thereby attenuating mortality risk related to the disease. COVID-19 vaccines have moreover been proven to lower the chances of COVID-19 patients developing post-acute sequelae of COVID-19 (PASC). PASC, also called ‘long COVID’ is a condition characterised by the persistence of COVID-19 symptoms months and even years following the infection, severely hampering a patient’s quality of life (QoL).

Unfortunately, unlike some vaccines which offer life-long protection against the associated disease (e.g., measles and hepatitis B), research has found that memory T and B cells related to antibody production against COVID-19 rapidly deteriorate, leading to lack of vaccination efficacy in as short as 120 days following initial vaccination. This demerit is compounded by the rapid rate at which SARS-CoV-2 mutates, leading to quite a few strains with reduced vaccine efficacy or outright vaccine immunity. These aspects necessitate follow-up COVID-19 vaccinations with ‘boosters’ updated to account for novel and emerging COVID-19 strains, including Omicron.

To handle this need, Pfizer and Moderna developed updated mRNA vaccines designed to perform against each ancestral and Omicron SAR-CoV-2 strains, which the US Food and Drug Administration (FDA) approved for emergency authorization use (EUA) and the Centres for Disease Control and Prevention (CDCP) subsequently beneficial for public consumption. Unfortunately, despite public awareness drives on the advantages of booster vaccines, this intervention uptake was stalled within the US, with lower than 20% of the eligible population taking a booster dose.

With a purpose to equip clinicians, policymakers, and most people with the knowledge required to more effectively curb COVID-19, this study investigates the explanations underlying the surprisingly low acceptance rates within the US.

Concerning the study

This study enrolled Americans participating within the Arizona COVID-19 Cohort (CoVHORT). This study group is longitudinal in methodology and is aimed toward investigating the long-term and acute effects of SAR-CoV-2 infection on Arizonans. CoVHORT participants included each individuals who had suffered from prior COVID-19 infections and those that had not. This study comprised a subset of 4827 participants chosen to best represent the American populace. Participants were recruited via online survey participation requests between February 13 and March 29, 2023.

Data collection involved recording demographic- and COVID-19-associated details, especially pre-existing health conditions, severity and symptoms of SARS-CoV-2 infection, COVID-19 test results, and health behaviors. The REDCap was used for survey design and administration. As and when required, additional COVID-19-specific research questionnaires were emailed to the relevant survey respondents. Surveys are administered at study enrollment and each subsequent three months, with data collection still ongoing.

“The survey asked the query: Have you ever received the updated (bivalent, omicron) mRNA booster from Pfizer or Moderna? If a “no” response was recorded, participants were asked to pick from an inventory of responses for not having received the booster; participants could select as many responses as were applicable.”

Three themes were identified a priori, which classified responses into three associated groups – 1. Bivalent vaccine knowledge, 2. Unclear in regards to the risks/advantages of vaccination/boosters, 3. Logistic concerns. Finally, statistical analyses focused on individuals who had received at the least the initial vaccination dose, excluding respondents who had never consumed a vaccine against COVID-19. Multivariable logistic regression (MLR) evaluation was used to discover trends between themes and demographic information (age, gender, education, race/ethnicity, and income). MLR models were adjusted for all of the listed demographic characteristics.

Study findings

Of the 4,827 individuals contacted, 2,298 (47.6%) accomplished all survey rounds, 2,196 of whom had received at the least one vaccination dose and were hence included in statistical analyses. Participants who accomplished the survey were on average, older (mean = 52.8) than those that didn’t (mean = 47.6), with all other demographic characteristics remaining statistically equal. This study represented a deviation from previous American vaccination reports, with 1,637 (74.5%) respondents receiving the second bivalent vaccination booster dose in comparison with lower than 20% of the final US populace.

Results revealed that individuals who received the booster vaccine were barely younger (mean = 50.5) than those that didn’t (mean = 52.8). Women (73.3%) and respondents of Hispanic ethnicity (12.6%) were less prone to take the booster dose than the general study cohort (70.0% and 9.7%, respectively). Education and income were found to significantly impact vaccine booster reception, with individuals at lower tiers of each quintiles of each characteristics less prone to receive the booster.

Of the 559 respondents who didn’t receive the booster, 39.5% claimed that prior COVID-19 infection and the perceived resistance conferred by the infection was the explanation for his or her aversion to the booster.

“The frequency of the remaining responses, so as of most-to-least reported, were as follows: I’m fearful about uncomfortable side effects (31.5%); I don’t think this booster will add more protection over the vaccines I’ve already had (28.6%); I’m fearful in regards to the safety of the booster (23.4%); I don’t think the booster will protect me from infection (23.1%); I don’t think the booster will protect me from severe disease or death (12.2%); I didn’t know I used to be eligible to receive it (11.8%); I didn’t understand it was available (10.0%); I don’t have time to get it (9.7%); I don’t know where to get it (7.5%); I didn’t know it was a brand new booster once I saw it advertised (6.6%); I’m fearful about taking time without work of labor to get the booster (6.1%); and I’m fearful about having the ability to pay for the booster (1.4%).”

Conclusions

In the current study, researchers investigated the underlying reason for many (>80%) of Americans refusing booster vaccines against COVID-19 using a cohort of 2196 individuals from Arizona as representatives. The evaluation revealed that misinformation about infection-conferred resistance (39.5%), and concerns about uncomfortable side effects (31.5%) of the vaccine were probably the most cited reasons for vaccine booster aversion. Concerns regarding booster safety (23.4%) and efficacy concerns (anti-COVID-19 effects [23.1%] and severe disease/death resistance [12.2%]) were the subsequent most cited underpinnings for low vaccine acceptance.

Knowledge in regards to the disease and vaccination effects were the least cited yet significant results of the survey. Nevertheless, education and income were found to play necessary roles in anti-COVID-19 vaccination as a complete and not only bivalent booster dose acceptance.

Based on these results, efforts to achieve out to the media and disseminate information would likely have the best impact on future vaccination drives, each for COVID-19 and disease outbreaks.

“In summary, the outcomes of this work provide support for continued efforts to advertise SARS-CoV-2 vaccinations and boosters amongst the USA population. Uptake of boosters continues to be well below the coverage needed for optimal protection of all people. The event of vaccines against SARS-CoV-2 occurred at an unprecedented speed, but implementation stays amongst the largest current public health challenges as updated boosters proceed to be developed and made available to the general public.”