Two new studies being presented at ACAAI 2021 reported that most people who think they will have an allergic reaction, or who believe they have had an allergic response to the first vaccine, can safely be fully vaccinated.

The first study looked at the charts of 100 patients who listed polyethylene glycol (PEG) as an allergy. PEG is an ingredient in the mRNA COVID-19 vaccines, and people are often asked if they have a PEG allergy prior to receiving an immunization. “Despite their previous reactions to PEG in oral PEG preparations, all 100 patients tolerated the full vaccine series without allergic symptoms,” says Mitchell Pitlick, MD, ACAAI member and lead author of the study.

Of the 100 patients, 64 received the Pfizer vaccine, 33 received the Moderna vaccine and 3 received the Janssen (J&J) vaccine. “Our cohort consisted primarily of patients who experienced gastrointestinal intolerance with an oral PEG preparation,” said allergist Miguel Park, MD, ACAAI member and co-author of the study. “This is unlikely to represent a true PEG allergy and shouldn’t delay vaccination. It’s important to recognize true vs. non-allergic reactions.”

The second study examined medical records of 25 patients referred to an allergy clinic who had reported Adverse Events Following Immunization (AEFI) to one of the mRNA COVID-19 vaccines. “Of the 25 patients, 23 experienced adverse symptoms following the first dose of the mRNA COVID-19 vaccine,” said allergist Benjamin St. Clair, DO, ACAAI member and lead author of the study. “16 had immediate reactions, 6 of 16 underwent skin testing with no positive results. With directed testing or other assessments, 15 underwent a vaccine challenge with only mild, expected post-vaccine symptoms.”

Only 2 of the 8 remaining patients with adverse symptoms following the first dose were advised by the allergist not to receive the second dose. “This study shows that with appropriate specialty evaluation by an allergist, the majority of patients with AEFI can tolerate the second dose of the mRNA vaccine to complete the series.” says Dr. St. Clair.