Given the small risk of severe allergic reaction and its treatable nature, the risk of catching the coronavirus and becoming severely ill or dying far outweighs that of a potential allergic reaction, CDC officials said.
The virus is killing roughly 2,670 people every day — an average that continues to rise, according to statistics compiled by The Washington Post.
“The known and potential benefits outweigh the known and potential risk of getting vaccine,” Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, said in a news briefing. Messonnier said CDC officials are worried about people being reluctant to be vaccinated — including health-care workers who were in the first-priority group for vaccinations.
Messonnier highlighted the rigorous approval process the vaccines underwent to be proved safe and effective. The two authorized vaccines — from Pfizer-BioNTech and Moderna — are “very safe” and severe allergic reactions are “still a rare outcome,” Messonnier said.
All vaccines carry a rare risk of potentially life-threatening allergic reaction, known as anaphylaxis. For the flu vaccine, the risk of anaphylaxis is 1.3 per 1 million vaccinations. The risk is higher but still relatively small with coronavirus vaccines at 11.1 cases of anaphylaxis per 1 million vaccinations, according to the CDC’s report.
Anaphylaxis can be quickly reversed with medicines including epinephrine, which is what was used to treat almost all of the 21 coronavirus vaccine recipients who had severe allergic reactions. Since the two-week period covered by the study, a handful of other allergic reactions have occurred, bringing the total to 28, CDC officials said.
The small number of cases makes it hard to draw conclusions about who may be at risk, but of the 21 cases studied, 17 of the people had a documented history of allergies or allergic reactions, and seven had a history of anaphylaxis. Of the 21 patients with allergic reactions, the median age was 40.
Almost all of the patients developed symptoms within 15 minutes of receiving the vaccine.
That is why the CDC recommends that patients linger for 15 minutes at the site where they have received the vaccine. For people with a history of severe allergic reactions, the recommended waiting time after vaccination is 30 minutes.
“The good news is how rare these allergic reactions are and how readily recognizable and treatable they are,” said Paul A. Offit, a vaccine expert at Children’s Hospital of Philadelphia and member of an external vaccine advisory committee to the Food and Drug Administration. “Yes, there’s an extremely small risk, but not a single person has died from the allergic reaction, while plenty of people have died from the virus.”
But experts remain concerned that initial reports of allergic reactions will dissuade some in the public from getting the shot.
“We as humans tend not to be very smart at assessing risk. We see doing something as more risky than not doing anything,” Offit said. “But the risk of adverse reaction is so small. People have a higher chance of getting hurt driving to the clinic for a shot than from the shot itself.”
The Pfizer-BioNTech vaccine was the only one being administered to the public during the two-week period included in the study, but CDC officials said their findings and recommendations are the same for the vaccine from Moderna, which is made using a process similar to the Pfizer shot. There has been one known case of allergic reaction to the Moderna vaccine, CDC officials said.
The Pfizer and Moderna vaccines have passed strict safety reviews. During randomized trials, no volunteers had severe allergic reactions, although people with a history of anaphylaxis were excluded from the trials. The issue of anaphylaxis produced headlines after health-care workers in the United Kingdom began receiving the Pfizer vaccine. Two health-care workers in the U.K. who had severe reactions had histories of anaphylaxis.
It was a third case of anaphylaxis, involving a health-care worker in Alaska, that many experts are focused on. The woman, described only as middle-aged and an employee of Bartlett Regional Hospital in Juneau, suffered multiple episodes of anaphylaxis, each requiring medical treatment with epinephrine and other medication before she recovered. That woman had no history of allergic reactions.
It is unclear what component in the vaccine might be responsible for the allergic reaction. Officials at the National Institutes of Health are rushing to devise a study to find that out. Last month, NIH officials announced the broad outlines of their study.
The goal is to identify the vaccine ingredient most likely to be responsible. Researchers hope to get an answer within a matter of weeks, but they face significant challenges. The study will recruit volunteers who have had a history of severe allergic reactions and who will receive the vaccine under close clinical supervision.
One suspected component cited by experts is a chemical widely used in medicines, cosmetics and other household products and that is part of the vaccine formula: polyethylene glycol.
The vaccines do not contain the coronavirus itself, but rather synthetic messenger RNA that instructs cells to manufacture a protein that looks like the spike protein on the coronavirus. The immune system responds by producing antibodies to that protein, creating sentries against infection by the real virus. The RNA does not interact with or alter a person’s DNA.
Milder side effects, such as headaches, fatigue or pain at the injection site, are common among coronavirus recipients and pass within a day or two, and signal that the vaccine is working to stimulate the immune system.