CDC Says Severe Reactions to Covid-19 Vaccines Are Rare

New data from the U.S. Centers for Disease Control and Prevention shows allergic reactions to Covid-19 vaccines are rare and anaphylaxis, one type of severe reaction, occurs in 2 to 5 people for every million vaccinated in the U.S.

The system hasn’t found any link between Covid vaccines and death, the CDC said on its website, and 41 million doses were administered in the U.S. through Feb. 7.

The latest data from the Vaccine Adverse Event Reporting System adds to a growing body of evidence on the safety of the shots. Watching for extremely rare side effects is an important element of the vaccine rollout, as inoculations that were tested in tens of thousands of people became authorized for millions more, and assurance of safety is key to uptake.

Covid vaccines “will undergo the most intensive safety monitoring in U.S. history,” the agency said on its website.

In the first days of the vaccination campaign in the U.S., a handful of reports of anaphylaxis raised concerns about how common the reaction might be. A known risk of vaccination, anaphylaxis occurs about 1.3 times per million doses of flu vaccine administered, and rates as high as 25 cases per million doses have been seen in small studies of other vaccines.

When anaphylaxis occurs, it is almost always within half an hour of administering the vaccine, the agency said. It can be quickly countered with antihistamines along with adrenaline injectors, and health workers giving the vaccine keep such items at the ready.

The Food and Drug Administration requires vaccine providers to report any deaths after vaccination, and the CDC investigates each death. The early waves of vaccinations went to nursing home residents and other older Americans. There were 1,170 reported deaths among people who were vaccinated, a rate of 0.003%, and no evidence suggests a link.

Mild Reactions

The CDC has emphasized that the newly authorized vaccines from Moderna Inc. and the partnership between Pfizer Inc. and BioNTech SE are safe. Both require two doses to provide full immunity, and rely on a technology known as messenger RNA, which has never before been used in an approved pharmaceutical product.

Covid-19 has killed more than 474,000 Americans to date. Trials of the vaccines from Pfizer and Moderna were more than 90% effective at preventing illness after two shots spaced either three or four weeks apart.

The CDC recommends that individuals who have had a severe allergic reaction to any ingredient in mRNA shots should not get vaccinated. Those who have had severe allergic reactions after the first dose should not return for their second, the agency has said.

Mild allergic reactions to the vaccines, such as hives, wheezing and swelling, can also occur, according to the CDC. Those who have had such a reaction to the first dose should also not get the second, the agency has said.

©2021 Bloomberg L.P.

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