Prevention and Attenuation of COVID-19 by BNT162b2 and mRNA-1273 Vaccines

Thompson, M. G.; Burgess, J. L.; Naleway, A.; Tyner, H.; Yoon, S. K.; Meece, J.; Olsho, L. E. W.; Caban-Martinez, A.; Fowlkes, A. L.; Lutrick, K.; Groom, H. C.; Dunnigan, K.; Odean, M. J.; Hegmann, K.; Stefanski, E.; Edwards, L. J.; Schaefer-Solle, N.; Grant, L.; Ellingson, K.; Kuntz, J. L.; Zunie, T.; Thiese, M. S.; Ivacic, L.; Wesley, M. G.; Mayo Lamberte, J.; Sun, X.; Smith, M. E.; Phillips, A. L.; Groover, K. D.; Yoo, Y. M.; Gerald, J. K.; Brown, R. T.; Herring, M. K.; Joseph, G.; Beitel, S.; Morrill, T. C.; Mak, J.; Rivers, P.; Poe, B. P.; Lynch, B.; Tao Zhou, Y.; Zhang, J.; Kelleher, A.

ABSTRACT BACKGROUND: Information is limited on messenger RNA (mRNA) BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 vaccine effectiveness (VE) in preventing SARS-CoV-2 infection or attenuating disease when administered in real-world conditions. METHODS: Prospective cohorts of 3,975 healthcare personnel, first responders, and other essential and frontline workers completed weekly SARS-CoV-2 testing during December 14 2020--April 10 2021. Self-collected mid-turbinate nasal swabs were tested by qualitative and quantitative reverse-transcription--polymerase-chain-reaction (RT-PCR). VE was calculated as 100%x (1-hazard ratio); adjusted VE was calculated using vaccination propensity weights and adjustments for site, occupation, and local virus circulation . RESULTS: SARS-CoV-2 was detected in 204 (5.1%) participants; 16 were partially ([≥]14 days post-dose-1 to 13 days after dose-2) or fully ([≥]14 days post-dose-2) vaccinated, and 156 were unvaccinated; 32 with indeterminate status (<14 days after dose-1) were excluded. Adjusted mRNA VE of full vaccination was 91% (95% confidence interval [CI]=76%--97%) against symptomatic or asymptomatic SARS-CoV-2 infection; VE of partial vaccination was 81% (95% CI=64%-90%). Among partially or fully vaccinated participants with SARS-CoV-2 infection, mean viral RNA load (Log10 copies/mL) was 40% lower (95% CI=16%-57%), the risk of self-reported febrile COVID-19 was 58% lower (Risk Ratio=0.42, 95% CI=0.18-0.98), and 2.3 fewer days (95% CI=0.8-3.7) were spent sick in bed compared to unvaccinated infected participants. CONCLUSIONS: Authorized mRNA vaccines were highly effective among working-age adults in preventing SARS-CoV-2 infections when administered in real-world conditions and attenuated viral RNA load, febrile symptoms, and illness duration among those with breakthrough infection despite vaccination.