Longitudinal assessment of COVID-19 vaccine uptake: A two-wave survey of a nationally representative U.S. sample.

Understanding factors that influence those who are initially COVID-19 vaccine hesitant to accept vaccination is valuable for the development of vaccine promotion strategies. Using Ipsos KnowledgePanel®, we conducted a national survey of adults aged 18 and older in the United States. We created a questionnaire to examine factors associated with COVID-19 vaccine uptake over a longitudinal period ("Wave 1" in April 2021 and "Wave 2" in February 2022), and utilized weighted data provided by Ipsos to make the data nationally representative. Overall, 1189 individuals participated in the Wave 1 survey, and 843 participants completed the Wave 2 survey (71.6% retention rate). Those who intended to be vaccinated as soon as possible ("ASAP") were overwhelmingly vaccinated by Wave 2 (96%, 95% CI: 92% to 100%). Of those who initially wished to delay vaccination until there was more experience with it ("Wait and See"), 57% (95% CI: 47% to 67%) were vaccinated at Wave 2. Within the "Wait and See" cohort, those with income <$50,000 and those who had never received the influenza vaccine were significantly less likely to be vaccinated at Wave 2. Among those who initially indicated that they would not receive a COVID-19 vaccine ("Non-Acceptors"), 28% (95% CI: 21% to 36%) were vaccinated at Wave 2. Those who believed COVID-19 was not a major problem in their community were significantly less likely to be vaccinated, while those with more favorable attitudes toward vaccines in general and public health strategies to decrease the impact of COVID-19 were significantly more likely to be vaccinated. Overall, barriers to vaccine uptake for the "Wait and See" cohort appear to be more practical, whereas barriers for the "Non-Acceptor" cohort seem to be more ideological. These findings will help target interventions to improve uptake of COVID-19 boosters and future novel vaccines.