Amanda Michaud MMS, PA-C
A major concern to public health officials is incomplete vaccination with the mRNA COVID-19 vaccine series. One reason for incomplete vaccination is if patients think that they have had allergic symptoms following the first dose of the vaccine. While the consequences of incomplete vaccination are not fully known, public health officials are concerned that it may lead to reduced vaccine efficacy and longevity. Thankfully, new research demonstrates that many patients with self-reported allergic symptoms after the first dose of an mRNA COVID-19 vaccine are likely to tolerate the second dose.
A large prospective study was completed at Mass General Brigham (MGB) and followed subjects who had the first dose of an mRNA vaccine. Subjects were followed for 3 days after the first vaccination and completed follow-up surveys via e-mail, phone, or text. Those with possible reactions were able to self-report allergic symptoms such as itching, rash, hives, swelling, and/or pulmonary symptoms. If symptoms were reported, subjects were able to consult with staff allergists at MGB. Of note, most of the subjects followed in this study were hospital employees.
Overall, 61,057 subjects received the first dose of an mRNA COVID-19 vaccine; 37% received the Pfizer-BioNtech vaccine, and 63% received Moderna. Of the 50,167 subjects who completed follow-up surveys, 1261 (2.5%) reported allergic symptoms within 3 days of their first vaccine dose.
Of the 1261 subjects who self-reported symptoms, 1218 were able to receive the second dose. Only 146 (17%) had recurrent symptoms, and none were severe. Of the subjects who self-reported allergic symptoms, 43 (3%) of them did not complete the vaccination series. The researchers concluded that patients who self-reported allergic symptoms were 5 times more likely not to complete the full vaccine series.
Another study completed jointly in the United States and Denmark followed patients who reported allergic symptoms after the first dose of the Pfizer-BioNtech mRNA COVID-19 vaccine. Of 77,602 healthcare workers who received the first dose, 47 were referred to allergy clinic for potential allergic reaction; 39 had history of mild reactions and were advised to complete the vaccine series, and 8 reported histories consistent with anaphylaxis. Of those 8 patients, thorough history was obtained and work-up completed, including skin testing for polyethylene glycol (PEG), which was negative for all 8. All 8 patients were given the second dose of the Pfizer-BioNtech vaccine and monitored in clinic, without any signs or symptoms of a recurrent anaphylactic reaction.
The findings in this second study suggest these reactions could likely be due to a non-immunoglobulin (Ig)E mechanism. In this case, pre-medication with a non-sedating antihistamine could help block the non-IgE histamine release and relieve symptoms in patients obtaining their second dose.
There have been numerous reports of suspected allergic reactions to the mRNA COVID-19 vaccines, and clinicians should be able to balance the risk of such reactions against concerns of incomplete vaccination. Based on study data, approximately 6.3 million US adults may experience allergic symptoms post-vaccination, and as many as 200,000 are at risk of incomplete vaccination. Providing proper counseling to patients with self-reported symptoms and referring to an allergy clinic, if necessary, is vital.