About one in a hundred thousand people who received the Pfizer-BioNTech COVID-19 vaccine had severe allergic reactions, U.S. health officials said Wednesday while emphasizing 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 following the administration of a reported 1,893,360 shots from December 14 to December 23.
“This is an average of 11.1 cases of anaphylaxis per one million doses administered,” senior CDC official Nancy Messonnier told reporters.
By comparison, influenza vaccines cause about 1.3 cases of anaphylaxis per million doses administered, and thus the rate of anaphylaxis for the Pfizer vaccine is about ten times greater.
Messonnier added that cases of anaphylaxis are still “extremely rare” and that it is in the best interests of people to take the vaccine, especially in the context of the COVID-19 pandemic which poses a much greater danger to their health. inhou.
“A good suggestion for someone to be vaccinated is the risk of COVID, and the bad results of COVID still outweigh the risk of a serious outcome through the vaccine,” she said.
“Fortunately, we know how to treat anaphylaxis, and we have made provision to ensure that people administering the vaccine at immunization sites are ready to treat anaphylaxis.”
The 21 cases were between 27 and 60 years old, with a mean age of 40, and all but two were treated with epinephrine.
Nineteen of the cases (90 percent) occurred in women, and the average onset time of symptoms was 13 minutes, but it ranged from two to 150 minutes.
Four (19 percent) of the patients were admitted to the hospital, including three in intensive care, and 17 (81 percent) were treated in an emergency department. It is known that all but one were discharged or repaired at home, and there were no deaths.
Symptoms include rash, feeling of throat, swollen tongue, hives, breathing problems, hoarseness, swollen lips, nausea and persistent dry cough.
Investigations are underway
The US has so far approved two vaccines for emergency use – one developed by Pfizer and the other by Moderna.
Both are based on the latest mRNA (messenger ribonucleic acid) technology and authorities have attached similar warning labels to both, recommending that people who have a known history of allergic reactions to the ingredients of the vaccines should not take them.
People with severe reaction to the first dose are also asked not to take a second dose.
Messonnier said investigations are underway to determine what could be the cause of the allergies.
There is not yet enough data to know the rate of anaphylaxis for the Moderna vaccine, which was approved a week after the Pfizer shot in the United States, or whether there will be a significant difference between the two vaccines. .
One preliminary hypothesis for the reactions is the presence of the compound polyethylene glycol (PEG), which has never been used before in an approved vaccine, but which is found in everyday products including laxatives, shampoos and toothpaste.
Both the Pfizer and Moderna vaccines use PEG molecules as part of the protective sheath around their main component, the mRNA that carries genetic instructions to cells.
© Agence France-Press