The vaccine effectiveness (VE) of both the Moderna and Pfizer-BioNTech mRNA vaccines declined at ≥120 days after the second dose, with higher VE and antibody levels for Moderna than Pfizer-BioNTech recipients, according to research published in the Dec. 10 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Kristina L. Bajema, M.D., from the CDC COVID-19 Response Team, and colleagues assessed the comparative effectiveness of the Moderna and Pfizer-BioNTech vaccines in preventing COVID-19-associated hospitalization at 14 to 119 days and ≥120 days after receipt of the second vaccine dose among 1,896 U.S. veterans during Feb. 1 to Sept. 30, 2021. Serum antibody levels to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were also compared among 234 fully vaccinated veterans without evidence of SARS-CoV-2 infection.

The researchers found that adjusted VE was 89.6 and 86.0 percent at 14 to 119 days after the second Moderna and Pfizer-BioNTech dose, respectively, and was 86.1 and 75.1 percent at ≥120 days for Moderna and Pfizer-BioNTech, respectively. Across all age groups and periods since vaccination, antibody levels were significantly higher among Moderna than Pfizer-BioNTech recipients; among recipients of both products, antibody levels declined between 14 to 119 days and ≥120 days.

"Continued monitoring of the effectiveness of COVID-19 vaccines alongside anti-SARS-CoV-2 antibody levels is needed to better understand the duration of protection of these vaccines and the correlation of antibody levels with protection," the authors write.

One author disclosed financial ties to the biopharmaceutical industry.