COVID-19 vaccine booster dose effectiveness among health workers: systematic review & meta-analysis

BACKGROUND: The COVID-19 pandemic still being a major public health issue. New vaccine products have been developed, approved, distributed and given primarily to Healthcare Workers (HCWs). The aim of this systematic review is to define the term of protection offered by the administration of EMA (European Medicines Agency)-approved COVID-19 vaccine booster dose for healthcare professionals, considering the Vaccine Effectiveness (VE) against SARS-CoV-2 infections. METHODS: A systematic research of the literature was carried out using PICO (Population, Intervention, Comparison, Outcomes) model and following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Then, a meta-analysis was carried out. RESULTS: Starting from 1241 obtained, 5 studies met the inclusion criteria. All studies dealt with only first booster dose. VE against infection was estimated, with Comirnaty booster dose, between 50% (95% C.I. 42-56%) and 86% (95% C.I. 79-90%) and, with Spikevax booster dose, between 56% (95% C.I. 45-65%) and 96% (95% C.I. 82-99%). The meta-analysis showed an overall VE of 73% (95% C.I. 70-76%). CONCLUSIONS: High VE levels among HCWs in the prevention of SARS-CoV-2 infections, which rapidly decline, were reported. Hence, the periodic administration of additional booster vaccine doses would be indicated. KEY MESSAGES: • EMA-approved COVID-19 vaccine booster doses are effective among healthcare workers, one of the categories most at risk: they can protect them from infections, keeping them able to work. • Due to the effectiveness short duration, periodic administration of additional booster doses would be indicated among healthcare workers.