Around 2% of those given Pfizer, Moderna vaccines reported mild allergic reactions: Study

According to the Boston-based study on health care workers, those that did report an adverse reaction recovered without major treatment.

A vial of the Pfizer-BioNTech Covid-19 vaccine | Photo: Kobi Wolf | Bloomberg File photo

New Delhi: A little over 2 per cent of people who received the first dose of Pfizer and Moderna’s mRNA vaccines reported mild allergic symptoms, according to a new study published in the peer-reviewed Journal of the American Medical Association (JAMA).

The Boston-based study also found that those who reported adverse reaction recovered without major treatment and the meantime to anaphylaxis onset (developing severe allergic reaction) was 17 minutes.

According to the study titled ‘Acute Allergic Reactions to mRNA COVID-19 Vaccines‘, the researchers studied the employees of the Boston-based healthcare firm, Mass General Brigham, who received mRNA vaccines from Pfizer and Moderna.

Of 64, 900 employees who received their first dose, 25,929 (40 per cent) received the Pfizer-BioNTech vaccine and 38,971 (60 per cent) received the Moderna vaccine. The acute allergic reaction symptoms solicited included itching, rash, hives, swelling, and/or respiratory symptoms.

“Acute allergic reactions were reported by 1,365 employees overall, more frequently with the Moderna vaccine compared with Pfizer-BioNTech,” the study said.

Anaphylaxis was confirmed in 16 employees — seven cases from the Pfizer-BioNTech vaccine and nine cases from the Moderna vaccine.

Allergic symptoms

According to the study, in this prospective cohort of healthcare employees, 98 per cent did not have any symptoms of an allergic reaction after receiving an mRNA COVID-19 vaccine.

“The remaining 2% reported some allergic symptoms; however, severe reactions consistent with anaphylaxis occurred at a rate of 2.47 per 10,000 vaccinations,” the study said.

According to another study published February, anaphylaxis to the mRNA Covid-19 vaccines is currently estimated to occur in 2.5 to 11.1 cases per million doses, largely in individuals with a history of allergy.

The researchers noted the difference.

“The incidence rate of confirmed anaphylaxis in this study is larger than that reported by the Centers for Disease Control and Prevention based on passive spontaneous reporting methods (0.025-0.11/10 000 vaccinations),” they said while quoting the February study.

“However, the overall risk of anaphylaxis to an mRNA COVID-19 vaccine remains extremely low and largely comparable to other common health care exposures,” they said.

Severe allergic reaction

The study highlighted that the mean age of individuals with anaphylaxis was 41 years. Out of 16 people who suffered anaphylaxis, the majority of them — 94 per cent — were females, 63 per cent had a prior allergy history, and 31 per cent had an anaphylaxis history.

“Meantime to anaphylaxis onset was 17 minutes.”

“One patient was admitted to intensive care, 9 (56%) received intramuscular epinephrine, and all recovered. Three employees, with prior anaphylaxis history, did not seek care,” the study said.