Effectiveness of COVID-19 mRNA vaccine booster dose relative to primary series during a period of Omicron circulation

During a period of Omicron variant circulation, we estimated relative VE of COVID-19 mRNA booster vaccination versus primary two-dose series in an ongoing community cohort. Relative VE was 66% (95% CI: 46%, 79%) favoring the booster dose compared to primary series vaccination. Our results support current booster recommendations.

mRNA COVID-19 vaccine effectiveness against SARS-CoV-2 infection in a prospective community cohort, rural Wisconsin, November 2020-December 2021

Reduced COVID-19 vaccine effectiveness (VE) has been observed with increasing predominance of the Delta variant. In a prospective rural community cohort of 1265 participants, VE against symptomatic and asymptomatic SARS-CoV-2 infection was 56% for mRNA COVID-19 vaccines.