Director, Epidemiology RTI Health Solutions Research Triangle Park, United States
Background: Monovalent booster or additional doses of COVID-19 (coronavirus disease 2019) vaccines were first authorized in the United States (US) in 2021, but their real-world effectiveness compared with a complete primary series without a booster/additional dose remains unclear.
Objectives: To evaluate the real-world effectiveness of receipt of a monovalent booster/additional dose of COVID-19 vaccine, by brand, compared with receiving a complete primary vaccine series without a booster dose in the US.
Methods: Brand-specific cohorts of “boosted” individuals aged 12-64 years (depending on brand-specific age authorizations during the study period) receiving a COVID-19 booster/additional dose after a complete primary vaccine series were identified in Optum pre-adjudicated administrative insurance claims data linked with Immunization Information Systems from 10 US jurisdictions. Individuals with a complete primary series but without record of a booster/additional dose were matched 1-to-1 to boosted individuals on calendar date, US county and state, and clinical factors. COVID-19 diagnoses were identified from claims in any medical care setting or in the hospital/emergency department (ED) setting. Propensity score–weighted hazards ratios (HRs) and 95% confidence intervals (CIs) were estimated by vaccine brand using Cox proportional hazards models; relative vaccine effectiveness (VE) was estimated as 1 minus the HR, overall and within variant-specific eras and subgroups.
Results: We identified 115,471 matched pairs for BNT162b2; 67,463 for mRNA-1273; and 1,718 for JNJ-7836735. Overall, for any medically diagnosed COVID-19, VE estimates ranged from 40% (JNJ-7836735) to 57% (mRNA-1273); against hospital/ED-diagnosed COVID-19, VE estimates ranged from 74% to 76%. VE was generally lower during the Omicron era than during the Delta era (e.g., for any medically-diagnosed COVID-19, VE ranged from 58% to 59% during the Delta era and ranged from 40% to 49% during the Omicron era).
Conclusions: Compared with a complete primary series without a booster/additional doses, the monovalent booster/additional doses provided additional effectiveness in real-world use for preventing medically diagnosed COVID-19, particularly hospital/ED-diagnosed COVID-19. Updated estimates of VE are needed in individuals receiving bivalent boosters and in time periods with new predominant viral variants.
