How the Development, Features and Roll-Out of a SARS-COV-2 Vaccine Shape Public Acceptance: A Conjoint Experiment in a Large Representative Sample of Danes

Background: While effective vaccines against the SARS-COV-2 virus have been developed and countries around the world have invested heavily to secure vaccine rollout, a fundamental challenge remains. How do policy-makers around the world ensure high vaccine uptake? What is lacking is a comprehensive assessment that captures a total spectrum of features related to the development of a vaccine, the vaccine's characteristics as well as the implementation of the vaccination program. Methods To provide such an assessment, we designed a conjoint experiment embedded in large-scale surveys based on a random sample from the central database of Danish social security numbers (N = 3,099), providing a sample that is representative for the adult Danish population. In the conjoint experiment, we vary features relating to three dimensions: 1) the stage of vaccine development, 2) the specific characteristics of the vaccine, and 3) the implementation of the vaccination strategy. Results We show that the features relating to characteristics of the specific vaccine have the strongest impact on vaccine acceptance. The features relating to vaccine development were the second most powerful, while the features relating to the implementation of the vaccination strategy were the least. Conclusions The public has a strong preference for vaccines with high efficacy. This may point to a mounting challenge for ensuring high vaccine uptake. Yet, the results also provide evidence that there might be a pathway to naturally alleviate this challenge. Thus, over time the “testing period” of the vaccines are naturally extended, which simultaneously implies an increase in vaccine safety (provided that the roll-out only reveals marginal side-effects). Our results suggest that such an increase in vaccine safety in itself will increase acceptance (in particular, if the roll-out only reveals marginal side-effects). Furthermore, the results indicate that vaccine acceptance can be increased if politicians leave it to the health authorities to communicate about recommendations.