Patient-reported data indicate certain factors, such as vaccine brand (mRNA-1273) and younger age, are associated with an increased risk for adverse effects following COVID-19 vaccination, but serious adverse effects are rare, according to a study published online Dec. 22 in JAMA Network Open.

Alexis L. Beatty, M.D., from the University of California in San Francisco, and colleagues used data from the online COVID-19 Citizen Science Study (March 26, 2020, to May 19, 2021) to identify 19,586 U.S. adults with at least one dose of the COVID-19 vaccine.

The researchers found that allergic reaction or anaphylaxis was reported in 26 participants (0.3 percent) after one dose of the Pfizer/BioNTech or Moderna vaccine and in 27 (0.2 percent) after two doses of the mRNA vaccines or one dose of the Johnson & Johnson (J&J) vaccine. The strongest factors associated with adverse effects were vaccine dose (two doses of mRNA or one dose of J&J versus one dose of mRNA: odds ratio [OR], 3.10), vaccine brand (Moderna versus Pfizer/BioNTech: OR, 2.00; J&J versus Pfizer/BioNTech: OR, 0.64), age (per 10 years: OR, 0.74), female sex (OR, 1.65), and having had COVID-19 before vaccination (OR, 2.17).

"Large digital cohort studies may provide a mechanism for independent postmarket surveillance of drugs and devices," the authors write.

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