Scientists Eye Potential Culprit Behind Covid-19 Vaccine Allergic Reactions

According to the Centers for Disease Control and Prevention, out of 272,001 doses administered through Dec. 19 six severe allergic reactions to the vaccine have been reported in the U.S.

As the vaccination process has started in many countries,  some of them have reported allergic reactions after being given a vaccine shot. Now, the Scientists are eyeing a possible culprit causing the allergies to the Pfizer Inc. and BioNTech SE Covid-19 vaccine: the compound polyethylene glycol, also referred to as PEG.

According to the Centers for Disease Control and Prevention, out of 272,001 doses administered through Dec. 19, six severe allergic reactions to the vaccine have been reported in the U.S. At least two cases of anaphylaxis have also occurred in the U.K. People in the U.S. began receiving Moderna Inc.’s vaccine on Monday, and no allergies thereto are reported so far .

In a statement, Pfizer said it “will closely monitor all reports suggestive of serious allergic reactions following vaccination.” “The company said its prescribing information includes a warning that “appropriate medical treatment and supervision should be readily available just in case of a rare anaphylactic event following the administration of the vaccine.”

Covid-19 Vaccine Allergic Reactions

Scientists are doubting on PEG as a potential suspect even as health authorities say they are still investigating the incidents and are planning to study the issue further. The compound is found in other drugs as well, and is known to trigger anaphylaxis on rare occasions.

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“Although, I think we’re just speculating here…it is understood that one among the components that’s present in both of the vaccines—polyethylene glycol—can be associated, uncommonly, with allergies ,” said Peter Marks, director of the Food and Drug Administration’s Center for Biologics Evaluation and Research, at a Dec. 18 press conference.

Adding that the FDA also plans to watch the Moderna vaccine rollout “very closely” since both vaccines contain PEG, he said, “What we’re learning now is that those allergic reactions could be somewhat more common than the highly uncommon that we thought they were because people do get exposed to polyethylene glycol in various pharmaceutical preparations.”

In both the Pfizer-BioNTech and Moderna vaccines, PEG is a component of the fatty cover that surrounds the messenger RNA , the most ingredient in the vaccine. Once the mRNA gets into cells, it teaches them to form a protein that resembles the spike protein found on the surface of the coronavirus. That induces a selected immune reaction that shores up the body’s defenses for when it’s exposed to the important virus.

The PEG-containing fatty envelope helps make sure the mRNA gets across the cell wall and into the cells.

Allergies to PEG are extremely uncommon, allergists and immunologists say, and it’s possible that the few people that had reactions after getting the Pfizer-BioNTech vaccine reacted to something else. The compound is found during a range of products, they say, like cosmetics, foods and medicines . Some vaccines also contain PEG-like compounds, they note.

Some sorts of PEG are more likely to cause allergies than others, scientists say.

“They’re beat an enormous large family, but in terms of their allergic potential, they’re not equal,” said Elizabeth Phillips, director of the middle for Drug Safety and Immunology at Vanderbilt University Medical Center. Types of PEG that are heavier are generally more likely to elicit allergies than others, she said.

At an equivalent time, “the PEG within the vaccines is different than what has been previously related to allergies ,” said James Baker, an immunologist who heads the Michigan Nanotechnology Institute for Medicine and therefore the Biological Sciences at the University of Michigan.

“The overall structure is extremely different from anything that’s been during a vaccine before,” he said. That makes it hard to inform how allergies to the PEG within the Covid-19 vaccines will compare to allergies to other PEGs, like those in certain laxatives, That have caused uncommon allergic reactions in the past.

Allergy experts say it isn’t certain yet whether the reactions seen so far were classic allergic reactions—that is, immune reactions involving an antibody called immunoglobulin E , or IgE, which are part of the so-called adaptive arm of the system , which learns to acknowledge specific intruders.

The reactions could also be due to a misfiring of the inherent immune system, causing a drop of reactions in what’s known as the body’s complement system.

“We need to check out all the chances,” said Dr. Baker.

Both he and Dr. Phillips recently attended a virtual meeting hosted by the National Institute of Allergy and Infectious Diseases to debate the Covid-19 vaccine allergies. The agency said it’s designing a study to seem more closely at the difficulty.

“We anticipate studying highly allergic individuals with prior episodes of anaphylaxis, also as another groups such [as] patients with known PEG allergy,” said Daniel Rotrosen, the director of the Division of Allergy, Immunology and Transplantation at NIAID, in an email.

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The study will include healthy individuals for comparison, he said, and researchers will gather biologic samples before and after vaccination to watch for any immune changes induced by the vaccine.

While PEG may be a possible culprit, “we got to keep an open mind regarding other possibilities,” he added.

For now, the CDC says people that have a history of severe allergies to any component of the Pfizer-BioNTech or Moderna vaccines shouldn’t receive the vaccine, and those who have a severe allergy after the primary dose shouldn’t receive the second.

The agency advises people with severe allergies to any other vaccine or injectable may receive the vaccine, but should speak with their medical providers before and about weighing the risks of an allergy with the advantages of receiving the vaccine.

There is no reason why people that have a history of mild or severe allergies to food, pets, oral medications or environmental allergens shouldn’t receive the vaccine, the CDC says.

The agency also say people that get the shots should be observed for quarter-hour after vaccination to watch for possible adverse reactions. People with a history of anaphylaxis should be observed for half-hour , it says.

The FDA requires that appropriate medical treatment for allergies be immediately available within the event of an acute, anaphylactic reaction.

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