What’s the Risk of Having a Severe Allergic Reaction to the COVID-19 Vaccine?

Severe allergic reactions to any type of vaccine are rare. Data from the American College of Allergy, Asthma & Immunology estimate that only 1.31 out of 1 million vaccine doses given will result in a severe allergic reaction, such as anaphylaxis.

With the new COVID-19 vaccines available, some people are worried that they could have an allergic reaction to the shot. However, research suggests that they likely do not need to be concerned.

A March study published in JAMA found that the vaccines are relatively safe, with only a small risk of a severe reaction from the mRNA vaccines.

The team of researchers from Brigham and Women’s Hospital in Boston tracked the health of hospital employees who received their first dose of an mRNA vaccine from December 16 to February 12, with a brief follow-up on February 18.

Research Focused on People Most at Risk

The researchers reviewed the medical history of employees who had two or more allergy symptoms, reported an allergic reaction, were of concern to doctors, and those referred by allergists and immunologists.

The researchers monitored the healthcare workers' post-vaccination status, including any allergic reactions. They conducted the monitoring via email, text messages, phone calls, and a smartphone app.

How Many People Had Allergic Reactions?

An employee was considered to have an acute allergic reaction if they showed signs of itching, rash, hives, swelling, or breathing problems. Of the 64,900 employees surveyed, 2.10% presented with an acute allergic reaction.

Anaphylaxis, a severe and sudden reaction that can include wheezing, vomiting, or hives, occurred in 0.025% of employees. There were seven cases from the Pfizer vaccine and nine cases from the Moderna vaccine. The researchers observed that the people who developed anaphylaxis were, on average, 41 years old. About 31% of them had a previous history of anaphylaxis.

Everybody Recovered

All of the employees in the study recovered after anaphylaxis. One patient had to seek intensive care, and nine were treated with an EpiPen.

In a press release for the research, Paige Wickner, MD, MPH, medical director of the Department of Quality and Safety at Brigham and Women's Hospital and senior co-author of the study, said that “the only allergy exclusion for vaccination was a prior episode of anaphylaxis to an inactive ingredient in the vaccine, called polyethylene glycol, or a cross-reactive inactive ingredient called polysorbate."

Wickner also provided reassurance that there were no long-term consequences for those who had reactions, stating that "all of our anaphylaxis cases recovered—no one had anaphylactic shock or required a breathing tube, even temporarily.”

What's the Average Person's Risk?

Reena Patel, MD, a board-certified medical doctor in family medicine and an urgent care physician at Garnet Health, says that the chances of developing severe allergic reactions are pretty low for an average person, but increase if you have had severe allergic reactions and anaphylaxis in the past.

“Data early on showed about 1 in 100,000 chance of having a severe reaction,” Patel tells Verywell. “You are at an increased risk for developing severe allergic [reactions] to a COVID vaccine if you have had a previous severe reaction to a vaccine or injectable therapy. The overall risk is still small, but in the group of people who did have a severe reaction, more than 70% had a previous history of severe allergies.”

The Importance of Post-Vaccination Monitoring

The study results also showed that severe allergic reactions tended to occur 17 minutes after vaccination. Anita Gorwara, MD, a family medicine physician and medical director of urgent care at Providence Saint John’s Health Center, tells Verywell that the findings track with the 15-minute observation period after vaccination.

Gorwara says that if people do not develop a severe reaction 15 or even 30 minutes after getting vaccinated, it's doubtful that they will develop a reaction days later.

“Doctors who are aware of a history of allergic reactions with vaccines in the past will monitor you for 30 minutes and make sure that you're safe to go home," Gorwara says. "It's not something that you have to worry about that it's going to happen two days later. If it happens, it's going to happen soon after you get the shot.”

Allergic Reactions to Vaccine Ingredients

According to Patel, people are more likely to develop a severe allergic reaction to vaccines with certain ingredients: polyethylene glycol (PEG) and polysorbate. If you have an allergy to either ingredient, ask your doctor about getting a different type of vaccine.

The Centers for Disease Control and Prevention (CDC) advises that if you are allergic to PEG, you might want to get the Johnson & Johnson vaccine. If you are allergic to polysorbate, either of the mRNA vaccines could be a better option.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.