As COVID-19 vaccinations roll out, a handful of people have experienced anaphylactic allergic reactions after receiving the Pfizer vaccine. These cases appear to be extremely rare, but the Centers for Disease Control and Prevention (CDC) advises several measures to recognize and respond to severe allergic reactions to the vaccine.
Thomas Clark, MD, MPH, deputy director of the CDC division of viral diseases, recently updated the situation at a Dec. 19, 2020, meeting of the CDC’s Advisory Committee on Immunization Practices (ACIP).
“As of Dec. 18, 2020, the CDC has identified six case reports of anaphylaxis following Pfizer-BioNTech vaccine,” Clark said. “Additional case reports have been reviewed and determined not [to be] anaphylaxis. These cases occurred within recommended observation window for vaccination and were promptly treated. Investigations are ongoing, although we do know that one case had a history of anaphylaxis following rabies vaccination.”1
Two cases occurred in healthcare workers in the United Kingdom. In addition, two U.S. healthcare workers, including one who needed intensive care, experienced severe allergic reactions after receiving the vaccination at the same hospital in Alaska.
“Persons with anaphylaxis have received vaccine from more than one production line,” Clark said. “Multiple lots have been distributed and are being used. You may have seen in the news a couple of cases in Alaska, but we have had reports from other jurisdictions and there is no obvious clustering geographically.”
Severe allergic reaction to any component of the vaccine is a contraindication to vaccination. Appropriate medical treatment must be immediately available in the event an acute anaphylactic reaction occurs following administration of the vaccine, Clark emphasized. Notification of these anaphylactic incidents has been timely, indicating the national surveillance for adverse reactions to the vaccine is working.
“Persons with anaphylaxis following COVID-19 vaccination should not receive additional doses of COVID-19 vaccine,” he said.
Also speaking at the ACIP meeting was Doran Fink, MD, PhD, an ex officio member of the panel representing the Food and Drug Administration.
“We are working closely with the manufacturer to identify what the causes of these reactions might be,” Fink said. “We will update the public in a timely manner if we find anything that would cause us to change the conditions of the emergency use authorization [EUA]. However, I want to stress at this time the totality of the data continues to support vaccination under the Pfizer EUA without any new restrictions.”
Contraindications to the Pfizer-BioNTech and Moderna COVID-19 vaccines include:
- Severe allergic reaction (e.g., anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components;
- Immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components (including polyethylene glycol [PEG]);
- Immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG).
“These persons should not receive mRNA COVID-19 vaccination at this time unless they have been evaluated by an allergist-immunologist and it is determined that the person can safely receive the vaccine under observation in a setting with advanced medical care available,” the CDC stated.2,3
The CDC considers a history of any immediate allergic reaction to any other vaccine or injectable therapy (unrelated to a component of mRNA COVID-19 vaccines or polysorbate) as a precaution but not a contraindication to vaccination for COVID-19. People with such a history should be counseled about the unknown risks of developing a severe allergic reaction and balance these risks against the benefits of vaccination.
“People with a history of allergies to oral medications or a family history of severe allergic reactions, or who might have a milder allergy to vaccines (no anaphylaxis), may also still get vaccinated,” the CDC advised.
All who receive a COVID-19 vaccine should be monitored on site. Those will a history of severe allergic reactions should be monitored for 30 minutes. All others should be monitored for 15 minutes after receiving the vaccine.
“Vaccination providers should have appropriate medications and equipment, such as epinephrine, antihistamines, stethoscopes, blood pressure cuffs, and timing devices to check pulse, at all COVID-19 vaccination sites,” the CDC stated. “Appropriate medical treatment for severe allergic reactions must be immediately available in the event that an acute anaphylactic reaction occurs.”
Because anaphylaxis requires immediate treatment, diagnosis primarily is based on recognition of clinical signs and symptoms, including:
- Respiratory: sensation of throat closing, stridor, shortness of breath, wheeze, cough;
- Gastrointestinal: nausea, vomiting, diarrhea, abdominal pain;
- Cardiovascular: dizziness, fainting, tachycardia, hypotension;
- Skin/mucosal: generalized hives; itching; or swelling of lips, face, throat.
“Early signs of anaphylaxis can resemble a mild allergic reaction, and it is often difficult to predict whether initial, mild symptoms will progress to become an anaphylactic reaction,” the CDC noted.
Patients who develop itching and swelling confined to the injection site should be observed closely for the development of generalized symptoms — beyond the recommended observation period, if necessary.
“If symptoms are generalized, epinephrine should be administered as soon as possible and emergency medical services should be sought,” the CDC emphasized.
- Clark T. Anaphylaxis following mRNA COVID-19 vaccine receipt. Dec. 19, 2020. https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2020-12/slides-12-19/05-COVID-CLARK.pdf
- Centers for Disease Control and Prevention. Interim clinical considerations for use of mRNA COVID-19 vaccines currently authorized in the United States. Updated Dec. 30, 2020. https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html
- Centers for Disease Control and Prevention. Interim considerations: Preparing for the potential management of anaphylaxis at COVID-19 vaccination sites. https://www.cdc.gov/vaccines/covid-19/clinical-considerations/managing-anaphylaxis.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fvaccines%2Fcovid-19%2Finfo-by-product%2Fpfizer%2Fanaphylaxis-management.html