evidence: Diverging from tested vaccination regimens without scientific evidence could undermine public confidence in vaccines against COVID-19 and the success of a global vaccination strategy to curtail the pandemic. [...] The global toll from COVID-19 has surpassed the grim milestone of 2 million deaths. Over one fifth of these deaths have occurred in the USA, with the highest per-capita mortality rate being in the UK. While these troubling statistics justify rapid action to vaccinate as many people as possible, deviating from a data-driven, clinically validated vaccine regimen is a risky approach that could derail current vaccination efforts, undermine public confidence in the vaccines and result in unintended long-term untoward consequences. Vaccination policies firmly grounded in scientific evidence must remain the mainstay of the global COVID-19 exit strategy. COVID-19 vaccines: acting on the evidence.