What People with Severe Allergies Need to Know About the COVID-19 Vaccine

COVID-19 vaccine

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As of Sunday, December 13, the Centers for Disease Control Prevention (CDC) said people in the U.S. with a history of severe vaccine reactions can still get the Pfizer/BioNTech vaccine. However, they should be monitored for 30 minutes afterward.

U.K. officials are warning people with severe allergies not to take the Pfizer/BioNTech COVID-19 vaccine after two people experienced anaphylaxis after receiving a shot. They have since recovered.

For the time being, people vulnerable to severe allergic reactions should not take the Pfizer vaccine, officials say.

“Any person with a history of anaphylaxis to a vaccine, medicine, or food should not receive the Pfizer/BioNTech vaccine,” June Raine, CBE, chief executive of the Medicines and Healthcare Products Regulatory Agency (MHRA) in the U.K., said in a statement.

Moncef Slaoui, PhD, who heads up Operation Warp Speed, expects the U.S. will recommend people with a history of severe allergic reactions refrain from getting the vaccine “until we understand exactly what happened” in the U.K. cases, according to a briefing on Wednesday.

The FDA granted the Pfizer vaccine emergency use authorization in the U.S. on Friday, December 11.

What This Means For You

If you have environmental allergies and haven't had a severe allergic reaction such as anaphylaxis, doctors don't expect you to experience any severe reactions from the COVID-19 vaccine.

Evaluating Pfizer Vaccine Data

In the U.S., trials didn’t include people with a history of severe allergic reactions.

A briefing document distributed at an FDA advisory panel meeting on Thursday noted that independently-conducted queries on the Phase 2 and Phase 3 all-enrolled safety population did show a slight numerical imbalance of adverse events that may be indicative of allergic reactions. In the vaccine group, 0.6% reported hypersensitivity-related adverse events, compared to 0.5% in the placebo group.

Stephen Powis, medical director for National Health Service in England, said investigators are working to determine if the reactions were due to the shot, according to the Associated Press.

Susan Wollersheim, MD a medical officer in the FDA’s Office of Vaccines Research and Review said the FDA has asked Pfizer to monitor people who received the vaccine for “anaphylactic reactions” as a potential risk after the reports out of the U.K.

What Is Causing Severe Vaccine Reactions?

“There must be a substance included in the vaccine that is causing a cross reaction to what the person has been allergic to in the past,” Amesh Adalja, MD, an assistant professor at the Johns Hopkins Bloomberg School of Public Health, tells Verywell.

“Each vaccine has unique ingredients and this may be something specific to the Pfizer version of the vaccine,” he says.

While some have speculated a stabilizing ingredient called polyethylene glycol (PEG) may trigger reactions when injected, so far, experts say there's no data to support this theory.

"The main ingredient I think people are suspicious of is something called PEG," Matthew Greenhawt, MD, member of the Asthma and Allergy Foundation of America’s (AAFA's) Medical Scientific Council, said in a panel meeting on Thursday. "We eat this. It is in a decent amount of food. Orally, this doesn’t really cause problems but injecting it was the one thing that came up, and people zeroed in on that. We have absolutely no causative data. We have absolutely nothing that says this did or didn’t cause it." 

The U.K. government is advising those with severe allergies to medication, foods, and other vaccinations to refrain from getting the vaccine for the time being. This also includes individuals who are prescribed epinephrine pens, Adalja explains.

“This does not apply to people who have seasonal allergies or those who have mild allergies when they are around certain animals such as cats,” he says.

Severe allergic reactions usually occur in the immediate period of time after the vaccination, within hours.

“We do not know if this would occur only after the first dose because individuals outside of the clinical trial have only gotten first doses,” Adalja says. “I would not advise someone who had a severe allergic reaction after the first shot to go on to get a second shot."

Adalja expects that the FDA will issue some guidance on vaccinating people with severe allergies.

How Common Are Severe Reactions After Vaccination?

“Severe allergic reactions to vaccines occur in a little over one in one million [people], so this is not unexpected as we move to vaccinate the general population from smaller clinical trials,” Adalja says. “This does not in any way erode my confidence in this vaccine.”

Stacey Galowitz, DO, an allergist and immunologist in New Jersey, tells Verywell that both anaphylaxis and anaphylactoid reactions are more likely to occur in people who have a previous history of allergic reactions.

Anaphylactic and anaphylactoid reactions differ due to the mechanism behind them, Galowitz explains. Both have rapid symptoms that can include a blood pressure drop, swelling, trouble breathing, and hives.

“Anaphylactic reactions following vaccines are rare, occurring at a rate of approximately one per million doses for many vaccines,” she says.

She notes that people with environmental allergies or mild reactions to food or medication should not have anxiety about the vaccine, since they don’t fall into the category of those having a significant allergic reaction, or anaphylaxis.

Galowitz says that though we don’t have all the safety information for future vaccines, there may be different active or inactive components that may be safer for those with specific allergies.

“Acute allergic reactions following vaccinations can be caused by the vaccine antigen, residual animal proteins, antimicrobial agents, preservatives, stabilizers, or other vaccine components,” she says.

According to Galowitz, initial reactions do not predict future reactions. People who are not initially allergic, but who develop an allergy after being sensitized, may be fine with the first dose and have an adverse reaction upon receiving the second dose.

“From a benefit/risk standpoint, people with known severe allergic reactions may inevitably be advised that if they were to receive [the vaccine], it should be administered in a setting where epinephrine and equipment for managing an airway was available for immediate use,” Galowitz says.

More Data Needed

Vincent C. Tubiolo, MD, an allergist in California, tells Verywell it is still too early to tell why the two individuals in the U.K. reacted or what type of reactions occurred. More data is needed, he says.

“In general, vaccines are unusual causes of allergic responses,” he says. “But the ingredients in vaccines can be a problem for some people.”

Most severe allergic reactions would normally occur within two to three hours after injection. Delayed reactions are also possible, Tublio says.

“As side effects are identified and effectiveness is reviewed, it is likely that the vaccines will become safer and more effective with appropriate modifications,” he adds. “Because this is new technology, it will be hard to answer the questions about timing and distribution of any modified vaccines. Based on what I have read from the FDA, it does not appear that the rare cases of allergic responses to the COVID-19 vaccines will affect the approval process.”

The Vaccine Will Only Get Safer

"There is always a way for someone who is allergic to a vaccine to get it 100% of the time. Our job is to figure out a way to get something into you safely that your body may not tolerate." Greenhawt said of the AAFA. "We are very good at treating reactions or hedging the risks . We’ll get to work on that if this is what needs to be done. We’ve done it before."

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