Uncertainty and unwillingness to receive a COVID-19 vaccine in adults residing in Puerto Rico: Assessment of perceptions, attitudes, and behaviors.

: Widespread vaccination against COVID-19 is essential to control the pandemic. Estimates of unwillingness and uncertainty toward COVID-19 vaccination and factors associated with it remain unclear among adults in Puerto Rico (PR).: To examine factors associated with uncertainty and unwillingness of COVID-19 vaccination among adults in PR.: The Health Belief Model was used to develop an online survey. Analyses included adjusted logistic regressions (aOR). A total of 1,911 adults completed the survey from December 2020 to February 2021.: Overall, 76.2% were females, 33.7% were aged 50 or older, and 82.7% reported an intent to get vaccinated. Individuals who did not perceive that their chances of getting COVID-19 were high (aOR = 2.94; 95%CI = 2.24-3.86), that getting COVID-19 was not a possibility for them (aOR = 2.86; 95%CI = 2.19-3.74), or unafraid of getting COVID-19 (aOR = 3.80; 95%CI = 2.76-5.23) had higher odds of uncertainty and unwillingness to get vaccinated against COVID-19. Participants who perceived that COVID-19 complications were not serious also had higher odds of uncertainty and unwillingness (aOR = 7.50; 95%CI = 3.94-14.3), whereas those who did not perceive that they would get very sick with COVID-19 had 89% increased odds. Those who agreed that they would only take the vaccine if many individuals took it had higher odds of uncertainty and unwillingness (aOR = 3.32; 95%CI = 2.49-4.43). The most reported reasons for uncertainty and unwillingness toward COVID-19 vaccination were vaccine safety (63.8%), efficacy (49.4%), and novelty (45.5%).: Although COVID-19 vaccination intent was high, the study highlights concern over vaccine safety and efficacy that should be addressed by public health campaigns and interventions to enhance vaccine uptake.