OBJECTIVES: To elucidate how Americans value COVID-19 vaccine characteristics, and determine whether their willingness to vaccinate is altered by the framing of the vaccination decision as altruistic or not.

METHODS: We conducted a discrete choice experiment (DCE) with Amazon MTurk participants randomized into a control group with standard DCE questions, versus a treatment group with questions framed altruistically. The survey consisted of demographic questions, an altruism index, and a DCE of 12 choice tasks with 3 profiles (Vaccine A, Vaccine B, and No Vaccination). Vaccine attributes included number of doses, efficacy in preventing infection, risk of severe disease, severe side effect type, risk of severe side effect, and subsidy. We estimated preference weights using multinomial logit models, controlling for framing, sex, age, political party, health status, race/ethnicity, and altruism score.

RESULTS: Sample included 2,014 respondents (control with no framing, n=1,037; altruism framing, n=977). Respondents preferred COVID-19 vaccines with allergic reactions vs neurological disorder as side effects (OR: 1.32; P <0.01), higher efficacy (OR: 1.03; P < 0.01), higher subsidies (OR: 1.00; P < 0.01), lower risk of side effects (OR: 0.99; P < 0.01), and lower risk of severe disease (OR: 0.99; P < 0.01). Preferences for single- vs double-dose formulations did not significantly differ (P > 0.01). Respondents with higher baseline altruism scores were more likely to prefer vaccination compared to those with lower altruism scores (RR: 1.83; P < 0.01). However, framing neither significantly affected preferences for vaccination nor modified the effect of baseline altruism on these preferences for vaccination.

CONCLUSIONS: Preferences were strongest for vaccines with less severe side effects, suggesting that innovators should prioritize COVID-19 vaccines with these characteristics. More altruistic individuals were more likely to vaccinate, but framing did not modulate vaccination decisions, implying its limited nudging effects for vaccination.