Comparative COVID-19 Vaccine Effectiveness Over Time in Veterans

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Understanding COVID-19 vaccine effectiveness in diverse patient groups is crucial for targeted vaccination strategies.
• Comparative effectiveness data is limited, particularly across different age groups and individuals with chronic health conditions.

Purpose of the Study:

• To compare the effectiveness of mRNA-1273 and BNT162b2 vaccines against coronavirus disease 2019 (COVID-19) in a large veteran population.
• To assess vaccine effectiveness over time and across different patient subgroups, including age and presence of chronic diseases.

Main Methods:

• A test-negative case-control design was employed using data from the US Department of Veterans Affairs COVID-19 Shared Data Resource.
• The study included 4.8 million veterans, analyzing vaccine effectiveness (VE) for symptomatic infections, hospitalizations, and ICU admission or death.
• Conditional logistic regression was used to estimate VE for two-dose mRNA vaccines (mRNA-1273, BNT162b2) and one-dose Ad26.Cov2.S, adjusting for covariates.

Main Results:

• Vaccine effectiveness for both mRNA vaccines declined over time and varied significantly by vaccine type and patient age (P < 0.01).
• mRNA-1273 demonstrated higher effectiveness than BNT162b2 against symptomatic infection, hospitalization, and ICU admission or death, particularly in individuals aged ≥65 years.
• mRNA-1273 also showed superior effectiveness compared to BNT162b2 in veterans with multiple chronic diseases.

Conclusions:

• mRNA-1273 was more effective than BNT162b2 in older veterans and those with chronic diseases, highlighting subgroup-specific vaccine performance.
• The findings underscore the importance of considering vaccine type and patient characteristics when optimizing COVID-19 vaccination strategies.