About one in 100,000 people who received the Pfizer-BioNTech COVID-19 vaccine have had severe allergic reactions, U.S. health officials said Wednesday, noting that the benefits of vaccination far outweigh the known risks.
The data comes from the Centers for Disease Control and Prevention (CDC), which documented 21 cases of anaphylaxis after the administration of 1,893,360 shots from Dec. 14-23.
“That makes an average of 11.1 cases of anaphylaxis for every million doses administered,” CDC senior official Nancy Messonnier told reporters.
In comparison, influenza vaccines cause about 1.3 cases of anaphylaxis per million doses administered, so the rate of anaphylaxis of the Pfizer vaccine is approximately ten times higher.
Messonnier added that cases of anaphylaxis were still “extremely rare” and it remains in the best interest of people to get the vaccine, especially in the context of the COVID-19 pandemic which poses a much greater danger to their health. .
“A good value proposition for someone getting vaccinated is the risk of COVID and the poor results of COVID are even more than the risk of a serious vaccine outcome,” he said.
“Fortunately, we know how to treat anaphylaxis and have established provisions to ensure that at immunization sites, people who administer the vaccine are prepared to treat anaphylaxis.”
All 21 cases ranged from 27 to 60 years, with a mean age of 40 years, and all but two were treated with epinephrine.
Nineteen cases (90%) occurred in women and the mean time to onset of symptoms was 13 minutes, but ranged from two to 150 minutes.
Four (19 percent) of the patients were hospitalized, including three in intensive care, and 17 (81 percent) were treated in an emergency department. It was known that all but one had been discharged at home or recovered at the time of the study and there were no deaths.
Symptoms include rash, tightness in the throat, swollen tongue, hives, difficulty breathing, hoarseness, swollen lips, nausea and persistent dry cough.
Ongoing research
The United States has so far authorized two vaccines for emergency use: one developed by Pfizer and the other by Moderna.
Both are based on the most advanced mRNA (messenger ribonucleic acid) technology, and authorities have attached similar warning labels to both, advising people with a known history of allergic reactions to vaccine ingredients. avoid taking them.
People who have a severe reaction to the first dose are also asked not to take a second dose.
Messonnier said research was being conducted to determine what may be the cause of the allergies.
There is still not enough data to know what the anaphylaxis rate is for the Modern vaccine, which was authorized in the U.S. a week after the Pfizer shot, or whether a significant difference will arise between the two vaccines.
A preliminary hypothesis for the reactions is the presence of the polyethylene glycol compound (PEG), which had never before been used in an approved vaccine, but which is found in everyday products such as laxatives, shampoos and toothpastes.
Both the Pfizer and the Modern vaccine use PEG molecules as part of the protective shell around their main ingredient, the mRNA that carries the genetic instructions to the cells.
© France-Presse Agency