Using cluster analysis to explore COVID-19 vaccine booster hesitancy by levels of medical mistrust in fully vaccinated US adults

Background: Underlying causes of vaccine hesitancy could significantly affect successful uptake of the SARS-CoV2 vaccine booster doses during new waves of COVID-19. Booster rates among US adults are far below what is needed for immunity, but little is known about booster hesitancy among fully vaccinated adults and whether medical mistrust exacerbates barriers to uptake. Methods: A cross-sectional survey was completed among 119 adults in Philadelphia, PA who reported having received the primary SARS-CoV2 vaccine series but not a booster dose. Using the LaVeist Medical Mistrust (MM) Index, a k-means cluster analysis showed two clusters (Low MM, High MM) and differences in attitudes and perceptions about COVID-19 booster vaccines were assessed using F-tests. Results: Respondents were 62% Black and female; mean age was 41; 46% reported earning less than $25,000 and 53% had a high school education or less. Overall intention to get boosted was low (mean 3.3 on 0-10 scale). Differences in COVID-19 booster perceptions between those with High (n = 56) vs. Low (n = 59) MM were found, independent of any demographic differences. Most statements (7/10) related to reasons to not be boosted were significant, with those with High MM indicating more concern about feeling sick from the vaccine (F=-3.91, p≤.001), beliefs that boosters are ineffective for vaccinated people (F= −3.46, p≤.001), and long-term side effect worries (F=-4.34, p≤.001). Those with High MM were also more concerned about the adverse effects of the vaccine (F=-2.48, p=.02), but were more likely to trust getting information from doctors or healthcare providers (F= −2.25, p=.03). Conclusions: Results indicate that medical mistrust is an important independent construct when understanding current COVID-19 booster hesitancy. While much work has looked at demographic differences to explain vaccine hesitancy, these results suggest that further research into understanding and addressing medical mistrust could be important for implementing interventions to increase booster rates.