Understanding the determinants of acceptance of COVID-19 vaccines: a challenge in a fast-moving situation.

Michael Schwarzinger and colleagues' study1 on the determinants of COVID-19 vaccine acceptance or refusal, published in The Lancet Public Health, provides an interesting novel perspective that differs from those of the many general population surveys thus far reported.2 The authors' experiment, conducted in July, 2020, assessed the effects of various scenarios on participants' intentions to be vaccinated against COVID-19. These scenarios were constructed by varying the characteristics of hypothetical COVID-19 vaccines (efficacy, risk of severe side-effects, and country of manufacturer) and vaccination strategies (herd immunity target and place of vaccine administration). This design enabled them to distinguish between systematic outright rejection of future COVID-19 vaccines (regardless of their characteristics) and vaccine hesitancy, which was sensitive to these characteristics. Their results might therefore be important in terms of vaccination strategy. One of the most notable results of this study is that, assuming a campaign of vaccination administered at mass vaccination centres and with communication about the benefits of herd immunity, the investigators' behavioural model predicted that 29·4% (95% CI 28·6–30·2) of the French working-age population were likely to refuse COVID-19 vaccination outright, while vaccine hesitancy ranged from 9·3% to 43·2% depending on vaccine characteristics.