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

A close up of gloved hands preparing a syringe of COVID-19 vaccine with an older adult white woman with a mask blurry in the background.


Key Takeaways

  • A recent study found that most people have a low risk of developing a mild allergic reaction to the mRNA COVID-19 vaccines.
  • The risk of having a severe allergic reaction to the vaccine is even smaller but is more likely in people with a history of allergic reactions.
  • If an allergic reaction happens, it will likely be within 15 to 30 minutes after vaccination.

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.

Employees in the study who received the Moderna vaccine had slightly more acute allergic reactions (2.20%) than the people who received the Pfizer vaccine (1.95%).

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.”

Paige Wickner, MD, MPH

All of our anaphylaxis cases recovered—no one had anaphylactic shock or required a breathing tube, even temporarily.

— Paige Wickner, MD, MPH

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.

Anita Gorwara, MD

If it happens, it's going to happen soon after you get the shot.

— Anita Gorwara, MD

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.

What This Means For You

The COVID-19 vaccines are safe. There is only a minimal risk of developing a severe allergic reaction. However, if you have allergies, it's best to discuss vaccine options with your doctor.

Even if you do not have known allergies, healthcare workers are taking precautions. They will monitor you for any serious side effects for 15 minutes after vaccination. If you've had an allergic reaction to a previous vaccination, the observation period will be extended to 30 minutes.

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.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American College of Allergy, Asthma, & Immunology (ACAAI). ACAAI Updates to Guidance on Risk of Allergic Reactions to COVID-19 Vaccines.

  2. Blumenthal KG, Robinson LB, Camargo CA, et al. Acute allergic reactions to mRNA covid-19 vaccinesJAMA.

  3. Turner PJ, Ansotegui IJ, Campbell DE, et al. Covid-19 vaccine-associated anaphylaxis: a statement of the world allergy organization anaphylaxis committee. World Allergy Organization Journal.

  4. Centers for Disease Control and Prevention (CDC). Information about COVID-19 Vaccines for People with Allergies.

By Jocelyn Solis-Moreira
Jocelyn Solis-Moreira is a journalist specializing in health and science news. She holds a Masters in Psychology concentrating on Behavioral Neuroscience.