COVID-19 mRNA-1273 Vaccine Safety: Adverse Events of Special Interest

Results of a safety analysis published in Open Forum Infectious Diseases showed clinically meaningful associations between the COVID-19 mRNA-1273 vaccine and anaphylaxis, myocarditis, and pericarditis. However, there were no links found between vaccination and any other adverse events of special interest (AESI).

Researchers in Massachusetts conducted a noninterventional, large-scale, retrospective safety review of the COVID-19 mRNA-1273 vaccine using safety data from spontaneous adverse events (AEs) that were reported between December 2020 and December 2022. The researchers aimed to determine whether observed rates of certain AESI following vaccination exceeded that of expected background incidence rates. The rate and frequency of specific AESI was calculated per 1 million vaccine doses administered.

A total of 772,908,958 doses of mRNA-1273 were administered to individuals across 91 countries during the study period. In total, 2,517,669 AEs were reported following vaccination. The rate of reported AEs was 852.3 per 1 million vaccine doses administered, with the highest peak in AEs observed in May of 2021.

The majority of AEs were reported by individuals aged 18 to 64 years (70.4%) and among women (67.5%). In addition, 42% of patients who reported AEs had at least 1 underlying health condition prior to vaccination. The most common conditions were hypersensitivity (8.4%), hypertension (5.2%), COVID-19 infection (3.0%), asthma (2.7%), and food allergies (2.3%).

Overall, 83.4% of reported AEs were not considered to be severe, 49.0% were associated with reactogenicity, most occurred following receipt of the first vaccine dose, and 0.7% resulted in fatal outcomes. Of note, most AEs that led to a fatal outcome were reported by older adults (70.4%).

Among all reported AEs, 2588 (0.4%) were anaphylaxis episodes and 6702 (0.7%) were myocarditis or pericarditis episodes. The majority of anaphylaxis episodes were reported among women (73.6%) and predominantly occurred after receipt of the first vaccine dose. In regard to myocarditis and pericarditis, episodes were primarily reported after receipt of the second vaccine dose and most frequently occurred within 7 days of vaccination.

The overall rate of reported anaphylaxis episodes was 3.35 per 1 million doses administered, with the highest rate noted in adult patients (age range, 18-64 years; 3.79 per 1 million doses). For myocarditis and pericarditis, the rate of reported episodes was 5.68 and 2.89 per 1 million vaccine doses administered, respectively.

In regard to other AESI, the number of reported events varied across subgroups stratified by age and sex. Both the total number of AESI and the number of AESI reported across subgroups was below or compatible with the expected background incidence rate.

Limitations of this analysis include the spontaneous nature in which AEs were reported, insufficient patient-level data, potential confounding, and possible inaccurate estimations of mRNA-1273 exposure.

“[W]ith the exceptions of anaphylaxis, myocarditis, and pericarditis, this mRNA-1273 safety analysis found no evidence to suggest an increased risk of AESI,” the researchers noted. “Safety monitoring of mRNA-1273 and variant-containing vaccines is ongoing,” they concluded.

Disclosures: This study was supported by Moderna, Inc., and multiple study authors declared affiliations with pharmaceutical, biotech, and/or device companies. Please see the original reference for a full list of disclosures.

This article originally appeared on Infectious Disease Advisor