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Immediate Allergic Reaction to Second SARS-CoV-2 Vaccine Dose Less Likely to Happen After Reaction to First

Researchers found 99% of individuals who experienced an immediate allergic reaction to their first SARS-CoV-2 vaccine dose tolerated a second dose without a severe reaction

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Written by Kelsea Pieters on February 22, 2022
What You Need To Know

Patients who experienced an immediate allergic reaction, severe or otherwise, to a first COVID-19 shot are unlikely to experience the same reaction to a second dose. Researchers in Canada and the U.S., including at the University of Colorado Anschutz Medical Campus, assessed studies involving more than 1,300 patients who reacted immediately to a first dose and found that 99% of those patients did not experience the same thing a second time. 

Researchers from universities in Canada and the United States have found that patients who experienced an immediate allergic reaction of any kind to a first SARS-CoV-2 vaccine dose are unlikely to experience severe immediate allergic reactions to a second dose.

Study results, published today in JAMA Internal Medicine, build on work initiated in 2021 examining allergic reactions to the first SARS-CoV-2 vaccine dose.

In this most recent paper, researchers assessed 22 studies involving 1,366 patients who received second doses of any of the available SARS-CoV-2 vaccines after experiencing allergic reactions to first doses. Only 0.16% of patients involved experienced an immediate severe reaction to a second dose; more than 99% of individuals tolerated a second dose with no immediate severe response.

“What these results tell us is that, for individuals with concerns regarding allergic reaction, taking a risk with vaccination is better than risking getting Covid-19,” said Matthew Greenhawt, MD, University of Colorado School of Medicine professor, Children’s Hospital of Colorado clinician and study senior author. “Our job as allergists is to manage risk. Those concerned about an immediate allergic reaction can receive vaccination doses under allergist supervision, especially those worried about a second dose. Full vaccination is important in mitigating infection.”

Additionally, fewer than 5% of patients who experienced anaphylaxis after a first dose had the same reaction a second time. Overall, 13% developed non-severe, manageable immediate symptoms. No deaths were reported among individuals throughout the 22 studies analyzed.

“These findings show that the a history of immediate reaction, including severe immediate allergic reactions, to a prior SARS-CoV-2 mRNA vaccine does not guarantee another reaction to the next vaccine dose,” said Derek Chu, assistant professor of medicine at McMaster University, Hamilton, Ontario, Canada and study first author. “Our data support safe vaccination of these individuals in a setting with professionals who can manage allergic reactions.”

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Matthew Greenhawt, MD