COVID Shots Seem Safe for Hospital Staff With Allergy Risk

Kerry Dooley Young

November 04, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

An analysis of self-reported allergy risk and post-COVID-19 vaccination incidents — such as hives and angioedema — among the employees of a large medical system suggests these kinds of adverse reactions can be managed and may tend to lessen in severity with second doses.

The prospective study was conducted by Lily Li, MD, and colleagues and was published online October 26 in JAMA Network Open. The authors are affiliated with Mass General Brigham (formerly known as Partners HealthCare System), a Harvard-affiliated system that comprises 16 healthcare institutions in the northeastern United States.

The study included 52,998 Mass General Brigham employees who had received either the Moderna or the Pfizer-BioNTech vaccine. Of these, 51,706 participants (97.6%) recieved two doses; 474 participants (0.9%) reported having a history of high-risk allergy.

The risk for self-reported severe allergic reactions during the 3 days after vaccination was 1.3% among employees with a high-risk allergy history and 0.3% among those without such a history, the investigators report. High-risk allergy history was thus associated with an increased risk for severe allergic reactions after mRNA COVID-19 vaccination (relative risk, 4.96; 95% CI, 2.20 – 11.19; adjusted relative risk, 5.20; 95% CI, 2.30 – 11.75).

Cases of allergic symptoms lessened after the second shot, and severe reactions were rarely seen, Li and colleagues write.

"The overall results of the study point to the safety in general from an allergic standpoint for both of the mRNA vaccines," Li told Medscape Medical News in an interview.

Li and colleagues used data that had already been collected in connection with the administration of the COVID-19 shots.

Mass General Brigham had its employees complete a prevaccination allergy risk assessment, either online, by telephone, or in person. For employees who reported no history of a severe allergic reaction, there was a standard 15-minute observation period after administration of the vaccines. For those who had reported any history of a severe allergic reaction to an injectable medication, vaccine, or other allergen, such as to latex or to some type of food, the observation period was doubled to 30 minutes.

The authors note that the study is limited by the fact that it focuses on healthcare employees from one geographic region, so the findings may not be generalizable to other groups.

"However, given the thousands of individuals who were included in this study, the findings remain informative and highly relevant as mRNA booster vaccinations begin," they write.

The investigators note how concerns about potential allergic reactions had hampered use of vaccines during the H1N1 influenza A pandemic of 2009–2010. During that pandemic, concerns were raised about the safety of administering egg-containing immunizations to people with egg allergies. This "played a role in global vaccine hesitancy," Li and colleagues write.

"A large body of evidence subsequently emerged that indicated inactivated influenza vaccine to be safe for those with an egg allergy, and current national and international guidelines now recommend the administration of influenza vaccine to individuals with an egg allergy of any severity," they write.

At the request of Medscape Medical News, Michael Ganio, PharmD, senior director of pharmacy practice and quality at the American Society of Health-System Pharmacists (ASHP), reviewed the article by Li and colleagues. He said that because of the size of the study population, it provides insight into how known risk factors may contribute to reactions to the vaccines and that the study in general increases confidence in these shots.

But Ganio also noted that many of the Mass General Brigham employees who reported having no previous history of allergic reactions experienced one after receiving the vaccines.

Of the 52,524 employees who did not report having high-risk allergies, 964 experienced allergic symptoms to an initial dose. Of those, 62 experienced a severe reaction.

Of this group of 964 who experienced allergic symptoms, 908 received a second dose. Of those who received a second dose, 110 had allergic symptoms. One reaction was severe.

With the second dose, there were 938 cases of allergic symptoms among the 50,353 people who did not have a history of allergic reactions and who had not experienced one after an initial dose.

These results underscore the importance of monitoring patients for 15 or 30 minutes after they receive their shots, Ganio said.

"Just because you don't have a history doesn't mean you aren't susceptible to having a reaction," Ganio said. In the study, there "was a higher percentage for people who had a previous history, but that doesn't mean that it can't happen in others too."

Li received grant support from the National Institute of Allergy and Infectious Diseases. Her co-authors have received research funding from Massachusetts General Hospital and the National Institute of Allergy and Infectious Diseases. Several authors have financial relationships with industry, which are listed in the original article.

JAMA Netw Open. Published online October 26, 2021. Full text

Kerry Dooley Young is a freelance journalist based in Washington, DC. She is the core topic leader on patient safety issues for the Association of Health Care Journalists. Young earlier covered health policy and the federal budget for Congressional Quarterly/CQ Roll Call and the pharmaceutical industry and the Food and Drug Administration for Bloomberg. Follow her on Twitter at @kdooleyyoung.

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