COVID: 1 in 100,000 people have had severe reactions to the Pfizer vaccine

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An American study has established an estimate in the United States of the risks of serious allergic reactions during the administration of the Pfizer / BioNTech vaccine against COVID-19.

As for possible allergic reactions from messenger RNA vaccine, a study published by the US Centers for Disease Control and Prevention is reassuring on this issue. It states that approximately one in 100,000 people who have received the Pfizer-BioNTech vaccine have had severe allergic reactions, and notes that the benefits of vaccination far outweigh the known risks.

To reach this conclusion, the researchers documented 21 cases of anaphylactic shock, the most serious manifestation of allergy, following the administration of 1,893,360 injections from December 14 to 23. The 21 cases were between 27 and 60 years old (median age 40) and all but two were treated with epinephrine.

In addition, 19 of the cases occurred in women, and the mean time to onset of symptoms was 13 minutes, but ranged from two to 150 minutes. Four patients were hospitalized, three of them in intensive care and the other 17 were treated in an emergency department. All but one of the patients had recovered and sent home at the time of writing the study except one and no deaths were reported. Symptoms observed included rash, choking sensation (throat closing), swollen tongue, hives, shortness of breath, hoarseness, swollen lips, nausea, and persistent dry cough.

"On average, this represents a rate of 11.1 anaphylactic shock per million doses administered," Nancy Messonnier, a CDC official, told reporters. The agency recalls that, by comparison, influenza vaccines cause about 1.3 cases of anaphylaxis per million doses administered, so the rate of anaphylaxis from the Pfizer vaccine is approximately ten times higher.

But still, cases of anaphylaxis related to the Pfizer / BioNTech vaccine "are extremely rare and it is still in the interest of people to take the vaccine, especially in the context of the COVID-19 pandemic, which poses a much greater danger. for your health ". adds Nancy Messonnier.

Because this type of allergic reaction is well known. "We know how to treat anaphylaxis and we have arrangements to ensure that at vaccination sites, the people who administer the vaccine are ready to treat anaphylaxis," she says.

The United States has so far authorized two vaccines: Pfizers and Modernas, which require two doses a few days apart. Health officials have issued the same warnings: People with a history of allergic reactions to ingredients in vaccines should avoid them. And those who have had a severe reaction to the first injection are advised not to take the second.

Research is being done to determine what could be the cause of these allergies, knowing that there is not enough data yet to know what the rate of anaphylaxis of the Moderna vaccine is or if there is a difference between the two vaccines.

A preliminary hypothesis for these allergic reactions is the presence of a compound, polyethylene glycol (PEG). The latter has never been used in a vaccine before, but is found in a number of everyday products: laxatives, shampoos, and toothpastes. Both vaccines use PEG molecules as part of the protective coating around its main ingredient, mRNA, that transmits genetic instructions to cells.

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