Poster presented at the 41st Annual International Society for Pharmacoepidemiology Conference
Background: A US post-approval study [EUPAS43468] is ongoing to assess the safety of the original Pfizer-BioNTech monovalent COVID-19 vaccine (BNT162b2), using data from 5 health insurers participating in the FDA’s Sentinel System.
Objective: To estimate incidence rates (IR) of 26 safety events in a combined population of BNT162b2 vaccinees and unvaccinated comparators in an interim analysis, towards assessing the feasibility of the final comparative analysis.
Methods: Individuals aged ≥ 6 months who received a first, second, and/or third dose (in a primary series) of BNT162b2 between December 11, 2020 (first date of BNT162b2 original monovalent authorization), and April 18, 2023 (last date of authorization), were identified. Unvaccinated individuals were matched to BNT162b2 vaccinees (in a variable ratio of up to 2:1) on age, sex, US state, calendar time, and propensity score.
Study outcomes were based on those included in COVID-19 vaccine safety surveillance in the FDA’s Biologics Effectiveness and Safety (BEST) System and CDC’s Vaccine Safety Datalink and were assessed using diagnosis codes in predefined outcome-specific risk intervals. Follow-up was censored upon receipt of another brand of COVID-19 vaccine, disenrollment from the health plan, receipt of a later dose before the recommended dosing spacing, or death. IRs were estimated in the matched study population by combining events and person-time in the exposed and unexposed groups. IRs were estimated similarly among subgroups (i.e., immunocompromised [IC] individuals and individuals with a history of COVID-19).
Results: ~14.7 million BNT162b2 doses were eligible for the study population, before matching to unexposed comparators. ~13.0 million doses were included in the matched study population.
IRs in the matched study population ranged from 0.6 per 100,000 person-years (PYs) for acute disseminated encephalomyelitis (ADEM) to 698.9 per 100,000 PYs for venous thromboembolism (VTE). IRs in IC individuals ranged from 1.6 per 100,000 PYs (ADEM) to 1,790.1 per 100,000 PYs (VTE) and in those with a history of COVID-19 from 2.2 per 100,000 PYs (thrombotic thrombocytopenic purpura) to 1,176.5 per 100,000 PYs (VTE). In the study population, IC individuals, and individuals with a history of COVID-19, ≥5 events of each outcome were observed.
Conclusions: IRs of safety events of interest were within the range of background IRs reported in BEST, supporting the feasibility of the final comparative safety analysis. The number of events for each outcome in the study population, IC individuals, and individuals with a history of COVID-19 suggests that the final comparative analysis will be able to evaluate all outcomes robustly, including in each of these subgroups.
