Undervaccination and severe COVID-19 outcomes: meta-analysis of national cohort studies in England, Northern Ireland, Scotland, and Wales (15 January 2024)

Summary

Undervaccination—receiving fewer than the recommended number of Covid-19 vaccine doses—could be associated with increased risk of severe Covid-19 outcomes including hospitalisation or death compared with full vaccination. This study aimed to determine the factors associated with undervaccination and to investigate the risk of severe Covid-19 outcomes in people who were undervaccinated in each UK nation, and across the UK.

The authors found that rates of undervaccination against Covid-19 ranged from 32·8% to 49·8% across the four UK nations in summer 2022. They also concluded that undervaccination was associated with an elevated risk of severe Covid-19 outcomes.