Pfizer’s Covid-19 vaccine and allergies: How concerned should you be?

The decision by British drug regulators to recommend against use of the coronavirus vaccine made by Pfizer and BioNTech in people who have a history of severe allergic reactions has raised a number of concerns.

The regulators issued the warning after two health care workers, both with such a history, had a serious reaction, anaphylaxis, after receiving the vaccine on the first day it became available in Britain. Anaphylaxis can be life-threatening, with impaired breathing and drops in blood pressure that usually occur within minutes or even seconds after exposure to a food or medicine, or even a substance like latex to which the person is allergic.

Both workers were treated and have recovered, the regulators said.

British authorities have since clarified their concerns, changing the wording from “severe allergic reactions” to specify that the vaccine should not be given to anyone who has ever had an anaphylactic reaction to a food, medicine or vaccine. That type of reaction to a vaccine is “very rare,” they said.

Their update also said that a third patient had a “possible allergic reaction” but did not describe it.

Officials of the US Food and Drug Administration said Thursday that because of the British cases they would require Pfizer to increase its monitoring for anaphylaxis and submit data on it once the vaccine comes into use. A panel of expert advisers to the FDA voted Thursday to recommend authorizing the vaccine for emergency use but also expressed concerns about the need to track anaphylaxis. The agency usually accepts the experts’ recommendations, and the authorization is expected within days. Vaccinations could start next week in the United States.

The initial report on the British cases touched off alarm and confusion by advising that people who had ever had a “severe allergic reaction” to a food, drug or vaccine should not receive the vaccine. The nature of the reaction was not explained at first, leaving many people with allergies to food or bee stings wondering if the new vaccine would be safe for them.

But the regulators’ subsequent clarification specified that their advice applied to people who had ever gone into anaphylaxis. It urged people with a “history of serious allergies” to discuss it with their doctors “prior to getting the jab.”

Authorities also said the shots should be given only in settings equipped to resuscitate patients if needed, by giving injections of epinephrine, also known as adrenaline.

What is known so far?

The two health care workers in Britain had experienced anaphylaxis in the past because of food allergies, a Pfizer official said during the FDA meeting Thursday. Both carried EpiPen-type devices to inject themselves with epinephrine in case of such a reaction.

They needed epinephrine to treat their reactions to the vaccine, and both recovered.

British health authorities said they would continue to investigate. It is not known whether an ingredient in the vaccine caused the workers’ reactions.

People with a history of an anaphylactic reaction to any vaccine were excluded from Pfizer’s studies, company officials said at the meeting Thursday.

Among those who participated in the Pfizer trials, a very small number of people had allergic reactions. A document published by the FDA on Tuesday said that 0.63% of participants who received the vaccine reported potential allergic reactions, compared to 0.51% of people who received a placebo.

In Pfizer’s late-stage clinical trial, one of the 18,801 participants who received the vaccine had an anaphylactic reaction, according to safety data published by the FDA on Tuesday. None in the placebo group did.

If I have allergies, should I be concerned?

Dr. Anthony Fauci, the nation’s leading expert on infectious diseases, said Wednesday that the allergic reactions were concerning but most likely rare, the kind of effects that show up when a vaccine moves out of testing and into broader distribution.

“If I were a person that had an underlying allergic tendency, I might want to be prepared that I might get a reaction and therefore be ready to treat it,” Fauci said, in a webcast moderated by Dr. Sanjay Gupta of CNN, sponsored by Harvard and The New England Journal of Medicine.

Fauci acknowledged that the problem could turn out to affect a lot of people.

“That’s one of the reasons why it’s important to cover the waterfront with different vaccine platforms,” he said, adding, “If in fact we do find out that there is a consistent issue of a certain subset of people like those with allergic reactions, you’ll always have other vaccine platforms that you can use, and hopefully you will not see that with those other platforms.”

Should people with allergies avoid Pfizer’s vaccine?

Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia, said the initial, broad recommendation in Britain mentioning severe allergic reactions seemed to be an overreaction that could needlessly scare many people away from a desperately needed vaccine in the middle of a raging pandemic.

Millions of people in the United States are allergic to foods like eggs or peanuts, as well as medicines or bee stings, and have had reactions that were serious enough to lead doctors to advise them to carry epinephrine injectors. But that does not necessarily mean the vaccine is risky for them, he said. About 5% of children and 4% of adults in the United States have food allergies, according to the National Institute of Allergy and Infectious Diseases.

Fewer than 1 in 1 million recipients of other vaccines a year in the United States have an anaphylactic reaction, Offit said.

Those reactions are treatable and much easier to control than a severe case of Covid-19, he said.

Many people with allergies to foods, bee stings or medicines have received multiple vaccines without problems.

As a member of the FDA advisory panel that met Thursday, Offit voted in favor of authorizing the Pfizer vaccine. But during the panel’s discussion of allergic reactions, he said, “This issue is not going to die until we have better data.”

He said research should be done to find out whether an ingredient in the vaccine can cause allergic reactions and whether people with other allergies might be especially sensitive to it.

Dr. Moncef Slaoui, head of the government’s Operation Warp Speed program to develop vaccines, said Wednesday that he thought U.S. experts would also advise people who have had severe allergic reactions to avoid the vaccine until the cases in Britain were fully explained.

Dr. William Schaffner, an infectious disease and vaccine expert at Vanderbilt University, said, “I wish Dr. Slaoui hadn’t gotten ahead of his skis.”

He said recommendations about who should or should not get the vaccine would be made by expert advisory panels to the Centers for Disease Control and Prevention, which will be meeting Friday and this weekend.

Schaffner said it seemed unlikely that the main ingredient in Pfizer’s vaccine, genetic material called mRNA, would cause an allergic reaction.

Next week, the FDA’s advisory panel will vote on whether to recommend authorizing a second coronavirus vaccine that uses mRNA, made by Moderna. The Moderna and Pfizer vaccines are similar but not identical: They use different types of fat particles, for instance, to coat the mRNA.

Schaffner said he knew of no evidence that people with food allergies were more likely than anyone else to have a severe reaction to a vaccine.

“We’ve dealt with allergies to all kinds of medicines and vaccines in medical practice, and we can do that in this circumstance also,” Schaffner said. “Everybody needs to be trained to be able to deal with this and deal with it promptly. I think we can manage this.”