The COVID-19 pandemic has been characterized by misinformation, politicization of public health, and extreme differences in risk assessment. In two studies, we sought to understand factors that contribute to differences in people's understanding of the virus and associated risks. We found that conservative participants reported higher levels of acceptable risk, have lower risk estimates of activities, and endorsed more misinformation. Participants with personal health risk factors rated COVID-19 risks as higher, more reflective participants had lower acceptable risk levels, and impulsive participants endorsed more misinformation. In our second study, we also found that reflective participants were more likely to wear a mask, get vaccinated, and maintain social distancing, and that participants judged arguments about COVID-19 measures largely based on the claim rather than supporting reasons. By clarifying these individual differences, public health experts can more effectively create targeted interventions for at risk populations, and be better prepared for future outbreaks.