(129) Safety of Moderna’s mRNA-1273.222 bivalent omicron-containing vaccine: interim results from a US claims database cohort study

Background: Moderna is conducting active surveillance in administrative claims to evaluate potential risks of adverse events of special interest (AESI) following administration of the Spikevax bivalent (mRNA-1273.222), granted emergency use authorization (EUA) on August 31, 2022.

Objectives: To assess the risk of AESI following Spikevax bivalent vaccination to supplement routine public health safety surveillance.

Methods: This retrospective observational study used US healthcare claims data (HealthVerity) in adults ≥18 years to assess the risk of AESI following ≥1 dose of Spikevax bivalent (Sep 1, 2022 - May 1, 2023). The incidence rates (IR) of AESI following Spikevax bivalent were compared to IR following influenza vaccination and in those with medically-attended COVID-19.

Propensity score weighting was used to estimate the probability of receiving Spikevax bivalent conditional on measured covariates. Cox proportional hazards regression was used to assess the relationship between vaccination and AESI. Comparison to individuals with medically-attended COVID-19 were limited to weighted IR.

Results: There were 518,700 and 5,326,444 Spikevax bivalent and influenza vaccinated adults, respectively. Two cases of myocarditis were observed following Spikevax bivalent and 17 cases following influenza vaccination following administration, with a hazard ratio (HR) = 1.54, 95% CI: 0.32-7.34, indicating no increased risk of myocarditis following Spikevax bivalent. One case of pericarditis was observed following Spikevax bivalent, and 29 cases following influenza vaccination following administration, with a HR = 0.44, 95% CI: 0.06-3.33, indicating no increased risk of pericarditis following Spikevax bivalent vaccination.

There were 1,060,556 Spikevax bivalent vaccinated adults compared to 1,051,540 adults with medically-attended COVID-19. In the 1-7 days following index, the IR of both myocarditis and pericarditis was higher following medically-attended COVID-19 compared to the IR following Spikevax bivalent.

No increased risks or elevated IRs of any other AESI were observed following Spikevax bivalent.

Conclusions: No increased risk of myocarditis, pericarditis, or any other AESI following Spikevax bivalent compared to influenza vaccination was observed in this analysis. Additionally, the IRs of all AESI were substantially lower following Spikevax bivalent than IRs following medically-attended COVID-19.

The results of this analysis support the known safety profile of Spikevax bivalent. Future analyses will be conducted on more contemporary data, including signal evaluation for myocarditis and pericarditis through self-controlled risk interval analyses.