Most people with allergies should get Pfizer's coronavirus shot, according to the FDA

• The newly authorized Pfizer coronavirus vaccine appears to be safe for people with food or environmental allergies, the FDA said on Saturday.
• Two people in the UK reported severe allergic reactions after getting the shot.
• After careful consideration, the FDA decided not to include warnings against the vaccine for people with a history of severe allergies, since that's a large segment of the population and such complications didn't occur in clinical trials.
• Still, there's more to learn, and all vaccine distribution sites will be equipped to treat any allergic reactions that may occur, which the FDA will continue to closely monitor.

People with common allergies to foods or to things in the environment like pollen or dust probably don't have to worry about having a serious reaction to the just-authorized Pfizer coronavirus vaccine, the US Food and Drug Administration said during a press conference on Saturday.

Even people who've had a severe allergic reaction to food or to something in the environment in the past should be OK to get the shot, Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said during the briefing. FDA said that people who are allergic to the shot itself or to one of its ingredients shouldn't get it.

"We're telling people that unless they've had a severe allergic reaction to the vaccine or one of its components, they can receive it," Marks said.

FDA held the briefing to provide more information on Pfizer's coronavirus vaccine, after clearing the shot late Friday for emergency use in people 16 and older. In authorizing the vaccine, the FDA said it's generally safe and highly effective at preventing symptomatic cases of COVID-19, the disease caused by the new coronavirus.

The clarification for people with allergies came after two people in the UK with known, severe allergies had non life-threatening anaphylactic reactions soon after being injected with the vaccine. UK health officials said that people with a history of severe, or anaphylactic, reactions to vaccines, medicines, or food should not get the shot.

"I just want to reassure the public that, although there were these few reactions in Great Britain, these we're not seeing in the larger clinical trial data sets," Marks said.

The trial included people with common issues like asthma and food allergies, but excluded people with severe allergies to vaccines.

Allergies are common, but serious reactions to this vaccine are not

About 30% of the global population has seasonal allergies, 10% have drug allergies, and 8% of children worldwide have food allergies, according to the American Academy of Allergy, Asthma, and Immunology. In the US, 1 in 10 adults has food allergies, Food Allergy Research and Education reports.

Marks said that 1.6% of the population has had a severe allergic reaction to a food or something in the environment.

"We would really not like to have that many people not be able to receive the vaccine," he said.

That's why, after careful consideration, the agency decided not to include a warning about allergic reactions, outside of those to the vaccine itself and its components, in its fact sheets.

Still, all vaccination sites will have EpiPens, Benadryl, and hydrocortisone on hand to treat any potential reactions that pop up, which the agency will track.

"We have very good safety surveillance systems in place in conjunction with the Centers for Disease Control and Prevention, and we may have to modify things as we move forward," Marks said. "But for right now, we're comfortable with this [advice], and the extra piece of this is that centers will have the ability to treat allergic reactions."

Most of the components in the Pfizer shots are benign

Marks said people with a history of allergic reactions should still talk to their doctor, who can help them figure out if they may be allergic to one of the components in the new vaccine, including lipids, potassium, chlorine, salt, and sugar. A full list of the components is available here.

"None of those ingredients appear to be highly allergenic," Dr. Sanjeev Jain, a board-certified allergist, immunologist, and CEO of Columbia Allergy told Business Insider's Hilary Brueck, stressing that most of the chemicals in the new shot are quite benign.

He said there could be a few explanations, then, for why the two people in Britain experienced severe reactions. In rare cases, people can react to polyethylene glycol, a component of one of the ingredients.

It's also possible the people had "non-specific" mast cell reactions, or that something about the vaccine particles triggered the body's response to allergens.

Finally, the two people with reactions could have recently had an allergy treatment or come in contact with another allergen, which, in combination with the effect of a vaccine on the immune system, "sent it into overdrive," Brueck reported.

"The fact that their immune system got stimulated by the vaccine, that could have triggered a reaction," Jain said.