During December 14-23, 21 cases of anaphylaxis, a life-threatening allergic reaction, were reported after administration of the first dose of the Pfizer-BioNTech COVID-19 vaccine, or a rate of 11.1 cases per million doses, compared with 1.3 cases per million doses for the flu vaccine, officials from the Centers for Disease Control and Prevention (CDC) reported at a press conference.
The agency also reported on the findings in its Morbidity and Mortality Weekly Report (MMWR).
“The anaphylaxis rate for COVID-19 may seem high compared to flu vaccines, but I want to reassure you this is still a rare outcome,” said Nancy Messonnier, MD, Director of CDC’s National Center for Immunization and Respiratory Diseases, at the press conference. “That doesn’t mean we couldn’t see potential serious health events in the future,” she added, saying that the CDC and FDA are reviewing all serious adverse event reports.
“I also think it is important to remember that many adverse events following immunization are coincidental,” Messonnier said.
The findings were based on the first doses of the vaccine distributed in the United States following the decision by the U.S. Food and Drug Administration (FDA) to issue an emergency use authorization (EUA) for the Pfizer-BioNTech COVID-19 vaccine on December 11, 2020.
The vaccine is administered in two doses separated by 21 days.
As of December 23, 2020, a reported 1,893,360 first doses of the Pfizer-BioNTech COVID-19 vaccine had been administered in the United States, and reports of 4,393 (0.2 percent) adverse events after receipt of the Pfizer BioNTech COVID-19 vaccine had been submitted to the CDC. Among these, 175 case reports were identified for further review as possible cases of severe allergic reaction.
Based on the data, the CDC said providers should follow the agency's guidelines for COVID-19 vaccine administration. “Locations administering COVID-19 vaccines should adhere to CDC guidance for use of COVID-19 vaccines, including screening recipients for contraindications and precautions, having the necessary supplies available to manage anaphylaxis, implementing the recommended post-vaccination observation periods, and immediately treating suspected cases of anaphylaxis with intramuscular injection of epinephrine,” the CDC wrote in the MMWR.
