Severe allergic reactions to the Pfizer vaccine are ‘highly rare’, scientists say

US health officials said Wednesday that one in a hundred thousand people who received the Pfizer-BioNotech COVID-19 vaccine have severe allergies, adding that the benefits of vaccination significantly reduce the known risks.

The data comes from the Centers for Disease Control and Prevention (CDC), which documented 21 cases of anaphylaxis after reporting 1,893,360 shots between 14 December and 23 December.

“This is an average of 11.1 anaphylaxis cases per million doses,” Nancy Masonier, a senior CDC official, told reporters.

In comparison, flu vaccine-causing 1.3 anaphylaxis cases are administered per million doses, and therefore the rate of anaphylaxis is about ten times higher for the Pfizer vaccine.

Mesonier said cases of anaphylaxis were still “extremely rare” and it remains in the best interests of people to take the vaccine, especially in the context of the COVID-19 epidemic that poses a major threat to their health .

“A good value proposition to vaccinate someone is their risk from COVID and poor outcome from COVID still outweighs the risk of serious consequences from the vaccine,” she said.

“Fortunately, we know how to treat anaphylaxis, and we have made provisions to ensure that at vaccination sites, people administering the vaccine are ready to treat anaphylaxis.”

The 21 cases ranged in age between 27 and 60, with an average age of 40, and all but two were treated with epipherin.

Nineteen (90 percent) of the cases occurred in women, and the average onset time of symptoms was 13 minutes, but ranged from two to 150 minutes.

Four patients (19 percent) were hospitalized, three of whom were involved in intensive care, and 17 (81 percent) were treated in the emergency department. Everyone knew that they had been discharged from home at the time of the study or had died and that there had been no deaths.

Symptoms include rashes, sore throat sensation, tongue swelling, urticaria, difficulty breathing, hoarseness, swelling in the lips, nausea and frequent dry cough.

Investigation in progress

The US has so far authorized two vaccines for emergency use – one developed by Pfizer and the other by Modern.

Both are based on state-of-the-art mRNA (messenger ribonucleic acid) technology and authorities have attached similar warning labels to both, suggesting that people who have a known history of allergy to vaccine ingredients should avoid taking them.

Those who have a severe reaction to the first dose are also asked not to take the second dose.

Mesonier said the investigation was underway to determine what may have caused the allergy.

There is not enough data yet to know what the rate of anaphylaxis is for the modern vaccine, which was authorized in the US a week after Pfizer was shot, or whether a significant difference between the two vaccines would emerge.

An early hypothesis for the reactions is the presence of the compound polyethylene glycol (PEG), which has never been used in an approved vaccine before, but is found in everyday products including laxatives, shampoos, and toothpastes.

Both Pfizer and Moderna vaccines use PEG molecules as part of the protective coating around their main component, the mRNA that gives genetic instructions to cells.

© Agnes France-Presse


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