When and why do people change their minds in favor of vaccination? Longitudinal analyses of switching COVID-19 vaccination preferences

Vaccinations are a cornerstone of public health. However, reluctance to accepting vaccines is common. Using longitudinal data, we investigated which individual and contextual factors were associated with switching preferences from initial hesitancy or unwillingness toward acceptance of a first COVID-19 vaccination. 12,512 participants of a Dutch cohort study who initially indicated being hesitant or unwilling to get vaccinated were included (December 2020-June 2022). Cox regression was used to determine what sociodemographic factors (e.g., age), vaccination-specific beliefs (e.g., perceived efficacy) and contextual factors (e.g., stringency of COVID-19 measures) were associated with switching toward getting vaccinated. Analyses were stratified into (1) the active campaign phase (over time more people became eligible for vaccination), versus (2) the residual phase (everyone was eligible and could still get vaccinated). Over time, 86% of initially hesitant and 34% of initially unwilling participants got vaccinated or intended to do so. Switching was less likely for people aged 40-54y (adjusted hazard ratio [aHR] 0.76 [95%CI = 0.69-0.84]) in phase 1, while in phase 2 they were more likely to do so (aHR = 1.44; 95%CI = 1.08-1.92). In both phases, people were more likely to switch if they had positive beliefs about its efficacy (phase 1: aHR = 1.76; 95%CI = 1.70-1.83; phase 2: aHR = 1.65; 95%CI = 1.54-1.77), and perceived getting vaccinated as the descriptive norm (phase 1: aHR = 1.30; 95%CI = 1.26-1.34; phase 2: aHR = 1.19; 95%CI = 1.13-1.25). During stricter lockdown measures people were also more likely to switch (phase 1: aHR = 1.26; 95%CI = 1.25-1.28; phase 2: aHR = 1.09; 95%CI = 1.08-1.09). A majority of initially hesitant people changed their minds about vaccination during the pandemic. Preference switches in favor of vaccination were most strongly associated with beliefs about the vaccine's efficacy in preventing illness. This study underlines the importance of providing up-to-date, balanced information and decisional support for people to weigh the benefits and risks of getting vaccinated versus not getting vaccinated.