Comparison of Antibody Response Durability of mRNA-1273, BNT162b2, and Ad26.COV2.S SARS-CoV-2 Vaccines in Healthcare Workers

Abstract Importance There is a dearth of comparative immunologic durability data after COVID-19 vaccinations. Objective To compare antibody responses and vaccine effectiveness 8.4 months post-primary COVID-19 vaccination. Design Setting and Participants: In this cohort study of 903 healthcare workers who completed surveys about baseline characteristics and COVID-19 vaccine/infection history, 647 had antibody assays completed and were included herein. Exposure COVID-19 vaccination with mRNA-1273 (n=387); BNT162b2 (n=212); or Ad26.COV2.S (n=10); unvaccinated (n=10); or boosted (n=28). Main Outcomes and Measures The primary outcome was IgG anti-spike titer. Secondary/tertiary outcomes included IgG spike receptor-binding domain competitive antibody blocking ELISA pseudoneutralization against the USA-WA1/2020 strain, and vaccine effectiveness against COVID-19 infection. Antibody levels were compared using ANOVA and multiple linear regression. Results Mean age was 49.7, 75.3% were female, and mean comorbidities/patient was 0.7. Baseline variables were balanced (p>.05) except for immunosuppression (higher in boosted, p=.047), prior COVID-19 infections (higher with Ad26.COV2.S and unvaccinated, p<.001), and time since primary vaccination (higher with mRNA-1273 and BNT162b2 than Ad26.COV2.S, p<.001). Unadjusted median (IQR) IgG anti-spike titers (AU/mL) were 1539.5 (876.7-2626.7) for mRNA-1273, 751.2 (422.0-1381.5) for BNT162b2, 451.6 (103.0-2396.7) for Ad26.COV2.S, 113.4 (3.7-194.0) for unvaccinated, and 31898.8 (21347.1-45820.1) for boosted (mRNA-1273 vs. BNT162b2, p<.001; mRNA-1273, BNT162b2, or boosted vs. unvaccinated, p<.006; mRNA-1273, BNT162b2, Ad26.COV2.S, or unvaccinated vs. boosted, p<.001; all other comparisons, p>.05). Unadjusted median (IQR) pseudoneutralization percentages were 90.9% (80.1-95.0) for mRNA-1273, 77.2% (59.1-89.9) for BNT162b2, 57.9% (36.6-95.8) for Ad26.COV2.S, 40.1% (21.7-60.6) for unvaccinated, and 96.4% (96.1-96.6) for boosted (mRNA-1273 vs. BNT162b2, p<.001; mRNA-1273, BNT162b2, or boosted vs. unvaccinated, p<.028; mRNA-1273, BNT162b2, Ad26.COV2.S, or unvaccinated vs. boosted, p<.001; all other comparisons, p>.05). Adjusted anti-spike and pseudoneutralization comparisons of mRNA-1273 and BNT162b2 showed similar patterns (p<.001). Vaccine effectiveness was 87-89% for mRNA-1273, BNT162b2, and boosted, and 33% for Ad26.COV2.S; no group differences were statistically significant. Conclusions and Relevance Durability of antibody responses 8.4 months after COVID-19 primary vaccination was significantly higher with mRNA-1273 than with BNT162b2, however, vaccine effectiveness was equivalent. Antibody responses and vaccine effectiveness were lower but not significantly different for Ad26.COV2.S; given statistical uncertainty in the small Ad26.COV2.S group, clinically important effects cannot be excluded.