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About one in a hundred thousand people who have received the Pfizer-BioNTech COVID-19 vaccine has had severe allergic reactions, US health officials said on Wednesday while stressing that the benefits of the 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 injections reported from December 14 to 23.
“This represents on average a rate of 11.1 cases of anaphylaxis for a million doses administered,” Nancy Messonnier, head of the CDC, told reporters.
In comparison, influenza vaccines cause about 1.3 cases of anaphylaxis per million doses administered, and therefore the rate of anaphylaxis for the Pfizer vaccine is about ten times higher.
Messonnier added that cases of anaphylaxis were still “extremely rare” and that it remains in the best interests of people to take the vaccine, particularly in the context of the COVID-19 pandemic which poses a much greater danger to their health.
“A good value proposition for a person to get vaccinated is their risk of COVID and poor COVID results are always more than the risk of a serious vaccine outcome,” she said.
“Fortunately, we know how to treat anaphylaxis and we have arrangements in place to make sure that at the vaccination sites the people who administer the vaccine are ready to treat the anaphylaxis.”
The 21 cases were aged 27 to 60, with a median age of 40, and all but two were treated with epinephrine.
Nineteen of the cases (90 percent) occurred in women, and the median 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 sent home or recovered at the time of the study, and there were no deaths.
Symptoms included a rash, a feeling of closed throat, swollen tongue, hives, difficulty breathing, hoarseness, swollen lips, nausea, and a persistent dry cough.
Ongoing investigations
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 cutting-edge mRNA (Messenger Ribonucleic Acid) technology and authorities have attached similar warning labels to both, which advise people with a known history of allergic reactions to vaccine ingredients to avoid. to take them.
People who have a severe reaction to the first dose are also advised 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 what the anaphylaxis rate is for the Moderna vaccine, which was cleared in the United States one week after the Pfizer injection, or whether a significant difference between the two vaccines will appear.
A 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 toothpastes.
Pfizer and Moderna vaccines use PEG molecules as part of the protective envelope around their main ingredient, mRNA, which transmits genetic instructions to cells.
© Agence France-Presse
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