HealthDay News — Most patients with an immediate and potentially allergic reaction to the first dose of the Pfizer-BioNTech or Moderna mRNA COVID-19 vaccine tolerate a second dose, according to a research letter published online July 26 in JAMA Internal Medicine.

Matthew S. Krantz, M.D., from the Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues examined the safety of the second dose of the Pfizer-BioNTech or Moderna vaccine in those with a history of immediate and potentially allergic reactions to the first dose. Data were included for 189 participants with mRNA COVID-19 vaccine first-dose reactions: 130 to Moderna and 59 to Pfizer-BioNTech; 32 of these reactions met anaphylaxis criteria. One hundred fifty-nine of these participants received a second dose.

The researchers found that 47 of the patients (30 percent) received an antihistamine premedication before the second dose. All 159 patients tolerated the second dose, including 19 with first-dose anaphylaxis. Thirty-two of the patients (20 percent) reported immediate and potentially allergic symptoms that were linked to the second dose; these were self-limited, mild, and/or resolved with antihistamines alone.


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“Second dose tolerance following reactions to the first dose argues that either many of these initial reactions are not all truly allergic reactions, or supports an allergic, but non-immunoglobulin E-mediated mechanism in which symptoms can typically be abated with premedications,” the authors write.

One author disclosed financial ties to the pharmaceutical and medical technology industries.

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