Safety and reactogenicity of second booster doses for mRNA vaccines

Abstract

Achieving high and equitable vaccine coverage rates of primary series and first booster doses globally in people at greater risk of severe disease and death is the highest priority in the continued fight against COVID-19.1 However, waning vaccine effectiveness following primary series and first booster was observed at a time of widespread relaxation of public health and social measures, combined with immune evasion of the Omicron variant and its sub-lineages. Evidence from studies suggests that additional protection of the most vulnerable populations can be achieved through administration of a second booster dose, although the follow-up duration for these studies is limited.