The following is the summary of “Effectiveness of mRNA COVID-19 Vaccine Boosters Against Infection, Hospitalization, and Death: A Target Trial Emulation in the Omicron (B.1.1.529)” Variant Era published in the December 2022 issue of Internal medicine by  Ioannou, et al.

When it comes to protecting older, high-risk groups from the Omicron (B.1.1.529) variation, the efficacy of a third dosage of the Messenger Ribonucleic acid (mRNA) COVID-19 vaccine (booster dose) seems questionable. The purpose of this study is to analyze the vaccine effectiveness (VE) of mRNA booster vaccines against SARS-CoV-2 infection, hospitalization, and death during the Omicron era, stratifying results by booster type, main vaccine type, time since initial immunization, age, and comorbidity burden.

Conducted from 1 December 2021 to 31 March 2022, this matched-cohort study aimed to simulate a target trial of booster immunization versus no booster. Specifically, the Veterans Health Administration in the United States. The study included people who had received 2 doses of the mRNA COVID-19 vaccine at least 5 months prior. Booster monovalent mRNA vaccination (either BNT162b2 from Pfizer-BioNTech or mRNA-1273 from Moderna) vs. no booster immunization. Booster velocity evaluations. A total of 490 838 individuals were randomly assigned to 1 of 2 groups and observed for up to 121 days. The participants were mostly male (88%), averaged 63 years old (standard deviation =14.0%), and were evenly distributed across these demographic characteristics (mean, 79.8 days). After 10 days, the booster’s VE against SARS-CoV-2 infection was 43.3% (95% CI, 40.6% to 43.9%), against hospitalization due to SARS-CoV-2 was 53.33% (95% CI, 48.1% to 58.0%), and against mortality due to SARS-CoV-2 was 79.1% (95% CI, 71.2% to 84.9%).

Booster VE was comparable between BNT162b2 and mRNA-1273, as well as between age groups and primary vaccination regimens, but it was considerably higher with a longer time since primary immunization and a higher comorbidity burden.  Men make up the vast majority of the population.  In the Omicron era, booster mRNA immunization was very beneficial in reducing mortality and about as effective in reducing infections and hospitalizations. To reduce SARS-CoV-2-related mortality and morbidity, especially among those who already have a lot going on in their lives, researchers need to increase the present, suboptimal rates of booster immunization.