Study: Allergic reactions to COVID mRNA vaccines rare, manageable

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Allergic reactions to COVID-19 mRNA vaccines are rare and usually mild, says to study at the end of last week at JAMA network open.

Researchers at Stanford University conducted a study of 22 allergic reactions reported to the first 38,895 doses of Pfizer / BioNTech and Moderna COVID-19 vaccines administered to healthcare workers from December 18, 2020 to January 26, 2021 (less than six hundredths of a percent). Of all vaccinations, 80.6% were from Pfizer vaccine, while 18.7% were from Moderna. The study population was made up of 60% women, 64% whites, 2% blacks, 20% Asians, 16% under 50 and 54% 70 and over.

According to the national Vaccine Adverse Event Reporting System (VAERS), the rate of severe vaccine-related anaphylaxis, or severe allergic reaction requiring hospitalization, is 4.7 per million for Pfizer vaccine and 2.5 per million for Moderna. But the authors noted that VAERS tends not to capture mild or moderate allergic reactions to vaccines.

Women at greater risk of allergy

Of the 22 allergic reactions that occurred within 3 hours of receiving a dose of vaccine, 20 occurred in women. Symptoms indicating a possible allergic reaction included hives; swelling of the mouth, lips, tongue or throat; shortness of breath, wheezing, or chest tightness; and changes in blood pressure or loss of consciousness.

Seventeen of the 22 reactions met the diagnostic criteria for probable anaphylaxis. Three vaccinated people received epinephrine, a drug usually given for severe anaphylaxis. All of the patients recovered.

Fifteen of the 22 vaccinees with allergic reactions had a history of allergy to antibiotics (10), foods (9), drugs excluding antibiotics (8), or a combination of these. Five patients had a history of anaphylaxis, 3 of them with antibiotics, 1 with pork and 1 with peanuts.

Current guidance from the Centers for Disease Control and Prevention advises anyone who has had a severe allergic reaction to any component or the first dose of any of the COVID-19 mRNA vaccines to avoid further exposure to that. -this.

Opportunities for vaccine reformulation

In follow-up basophil activation testing, 10 of 11 vaccine blood samples reacted to the inert vaccine ingredient, polyethylene glycol (PEG), which is used in both Pfizer and Moderna vaccines (none has only tested positive via a skin test). Because all 11 vaccinated had antibodies to PEG in their blood, the authors said they were likely already susceptible to it from previous exposure.

“What’s important is what we didn’t find, as much as what we found,” said lead author Kari Nadeau, MD, PhD, in a Stanford article. Medicine. Press release. “It does not appear that the mRNA itself causes the allergic reactions.”

Study results also suggest that the reactions were mediated by antibodies and immunoglobulin G (IgG) basophils, which are typically managed with antihistamines, fluids, corticosteroids, and observation. This means that many vaccinees who had allergic reactions to the first dose will be able to safely receive the second dose under medical supervision, the researchers said.

“It’s nice to know these reactions are manageable,” Nadeau said. “Having an allergic reaction to these newer vaccines is rare, and if it does, there is a way to manage it.”

The study also suggests how vaccine makers can reformulate vaccines to make them less allergenic, Nadeau said. PEG is a common ingredient in household products, cosmetics, and drugs, to which women are likely more exposed than men, the researchers said. This could not only explain the gender difference in vaccine reactions, but it could also allow manufacturers to reformulate vaccines with fewer allergen stabilizers.

“If confirmed by more systematic future investigations, these results highlight potential opportunities for patient risk stratification and alternatives in vaccine manufacturing; In addition, they may inform the development of ongoing mRNA vaccines, including that of possible COVID-19 boosters to protect against emerging disease variants, the authors concluded.

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