Twenty-nine recipients of the COVID-19 vaccine in the United States suffered severe allergic reactions after receiving the injection, health officials said on Wednesday.
The Centers for Disease Control and Prevention said that anaphylaxis, a potentially fatal allergic reaction, occurred among recipients of the Moderna and Pfizer vaccines, although officials stressed that it was a “rare result” and no deaths were reported.
“As you can imagine, huge efforts are underway to understand what may be the cause of these allergic reactions,” Dr. Nancy Messonnier, director of the agency’s National Center for Immunization and Respiratory Diseases, told reporters.
Messonnier said they are still collecting information on all cases of anaphylaxis – particularly with the Modern vaccine, as it has been responsible for less than the 4.8 million doses administered so far.
The agency revealed in a report on Wednesday that there were 21 cases of anaphylaxis in 1.9 million people who received the first dose of the Pfizer vaccine.
Seventeen of the 21 people had a documented history of allergies or allergic reactions, seven of whom had previously suffered anaphylaxis, said Messonnier.
But the rate is higher than among people who received the flu vaccine.
Flu vaccines cause anaphylaxis in about 1.3 people per 1 million recipients, while about 11.1 Pfizer recipients in every million have had the reaction, the CDC estimates.
“You could say mathematically that it is ten times the value, but I think you missed the point because it is still extremely rare,” said Messonnier.
“We all expect any vaccine to have zero adverse events, but even in 11 cases for 1 million doses administered, it is a very safe vaccine.”
She added that the risk of getting COVID-19 or experiencing a bad virus result is even greater.
“Fortunately, we know how to treat anaphylaxis and we put measures at the immunization sites,” said Messonnier.
Anyone who has an allergic reaction to the first dose of the COVID-19 vaccine is not recommended to receive the second injection of the two-dose regimen, said Messonnier.
The agency is asking anyone with a history of allergy to see their doctor to determine whether to get the vaccine.
“There is a difference between someone who had a mild allergic reaction in childhood and someone who had a major allergic relationship last week,” said Messonnier.
“It will be important to have a doctor helping to exercise judgment instead of having strict and quick rules.”