RESUMO
BackgroundIntrinsic durability of immune responses elicited by COVID-19 vaccines will drive vaccine effectiveness long-term across settings and may differ by vaccine type. We aimed here to determine durability of protection of three COVID-19 vaccines BNT162b2, mRNA-1273 and Ad26.COV2.S following primary vaccination against breakthrough infections, hospitalisations, and intensive care unit (ICU) admissions in the United States (US). MethodsUsing national claims and laboratory data covering 168 million lives, we conducted a matched case-control study with fully vaccinated individuals between January 1 and September 7, 2021. Odds ratios (OR) for developing outcomes in months two through six following primary vaccination were estimated relative to the first month after primary vaccination for each vaccine separately. Results compare each vaccine to itself and are not directly comparative. Odds ratios were translated into vaccine effectiveness (VE) using assumptions about event rates in an unvaccinated cohort. FindingsRelative to its baseline, stable protection was observed for the single-shot Ad26.COV2.S against infections and severe disease. Relative to their baseline protection waned overtime against infections for BNT162b2 and mRNA-1273 and against hospitalisations for BNT162b2. No waning of baseline protection was observed at any time for ICU admissions for all three vaccines. Calculated baseline VE was consistent with the published literature. InterpretationWhile the starting protection level provided by the primary series may differ by vaccine type and mechanism of action, this study demonstrated by comparing each vaccine to its own baseline protection that the three vaccines in three separate populations may have different durability profiles. Further investigation is required to fully characterize the durability profile of the three vaccines. Moreover, as the COVID-19 pandemic continues, and as more countries and populations implement a standard of care consisting of three doses of the mRNA vaccines or two doses of Ad26.COV2.S, further investigation is critical to understand the level of protection and the durability of response over longer periods, novel variants and in response to homologous and heterologous boosting.
