Can a COVID-19 Vaccine Live up to Americans’ Expectations? A Conjoint Analysis of how Vaccine Characteristics Influence Vaccination Intentions

Objective: A vaccine for the novel coronavirus (COVID-19) could prove critical in establishing herd immunity. While past work has documented the prevalence and correlates of vaccine refusal, I assess how a less explored topic -- properties of vaccines themselves (e.g., national origin, efficacy, risk of side effects) -- might influence vaccination intentions. This information can help public health officials preempt differential vaccine demand, and inform health communication campaigns that encourage vaccine uptake. Rationale: Previous research suggests that Americans should be more likely to intend to vaccinate if presented with a US-made vaccine that carries a low risk of minor side effects, is highly effective, is administered in just one dose, and has spent significant time in development. Methods: I administered a conjoint experiment (N = 5,940 trials) in a demographically representative survey (N = 990) of US adults to assess how variation in vaccine properties influence self-reported public vaccination intentions. Results: I find that respondents prefer vaccines that are US-made, over 90% effective, and carry a less than 1% risk of minor side effects. This is potentially problematic, as some leading vaccine candidates are produced outside the US, and may be less effective and more likely to produce minor side effects than respondents would otherwise prefer. Worryingly, intended vaccine refusal rates exceed 30% for a vaccine meeting these optimal characteristics. Encouragingly, though, Americans show no clear preference for vaccines administered in one dose, or developed in under a year, and do not appear to draw a distinction between weakened viral vs. mRNA-based vaccines. Conclusion: Americans’ preferences for a novel coronavirus vaccine may be at odds with the vaccine that ultimately hits the market, posing both policy and health communication challenges for vaccination uptake.