Pfizer-BioNTech COVID-19 (left) and Moderna COVID-19 (right) vaccines.
Matic Zorman | Getty Images
The National Institutes of Health said Wednesday it has begun looking at why some people have suffered from severe allergic reactions shortly after receiving the Pfizer–BioNTech and Moderna Covid-19 vaccines.
“The public understandably has been concerned about reports of rare, severe allergic reactions to the Moderna and Pfizer-BioNTech COVID-19 vaccines,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which is part of the NIH, said in a statement.
“The information gathered during this trial will help doctors advise people who are highly allergic or have a mast cell disorder about the risks and benefits of receiving these two vaccines. However, for most people, the benefits of COVID-19 vaccination far outweigh the risks,” he said.
Medical experts say allergic reactions from vaccines are rare but can sometimes happen. Most of the rare, severe allergic reactions to the vaccines have occurred in people with a history of allergies, public health officials have said. An immediate allergic reaction usually happens within 4 hours of getting vaccinated and may include symptoms such as hives, swelling and wheezing, according to the Centers for Disease Control and Prevention.
The CDC said in January allergic reactions are occurring at a rate of 11.1 per 1 million vaccinations for the Pfizer shot and 2.5 per 1 million for the Moderna shot.
The NIH study will enroll 3,400 adults ages 18 to 69 at up to 35 academic allergy-research centers nationwide, the agency said. Participants will be divided into groups and be assigned at random to receive either the Pfizer-BioNTech vaccine, the Moderna vaccine, a placebo followed by the Pfizer-BioNTech vaccine or a placebo followed by the Moderna vaccine.
Alkis Togias, chief of the NIAID’s allergy, asthma and airway biology branch, told CNBC in December that researchers at the U.S. agency became interested in the rare phenomenon after reports that a few people had reactions to Pfizer’s vaccine that qualified as anaphylaxis, a severe and potentially life-threatening allergic reaction.
The CDC has been asking health-care providers to monitor patients for 15 minutes after vaccination and 30 minutes for those who have a history of allergic reactions.
If someone has a severe allergic reaction after getting the first dose of a Covid-19 vaccine, the CDC recommends that they do not get the second dose of that vaccine, even if the allergic reaction was not severe enough to require emergency care.