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Delaware Health Alert Network #445

April 5, 2021 2:10 pm

Health Alert

The Delaware Division of Public Health (DPH) is issuing this health alert to advise the medical community to be aware of allergic reactions to the COVID-19 vaccine that may be seen in people with a history of allergic reactions.


DPH is aware of confusion and concerns surrounding individuals with histories of severe allergic reaction and receipt of mRNA-based vaccines (i.e. Moderna and Pfizer-BioNTech COVID-19 vaccines).

Early nationwide safety monitoring of the Moderna COVID-19 vaccine detected 10 cases of anaphylaxis after administration of 4,041,396 first doses the vaccine (2.5 cases per million Moderna COVID-19 vaccine doses administered), as well as cases of less severe non-anaphylactic allergic reactions based on U.S. data for December 21, 2020 to January 10, 2021. An earlier analysis of the Pfizer-BioNTech COVID-19 vaccine estimated an initial rate of 11.1 cases of anaphylaxis per million doses administered after receipt of the first dose of the Pfizer-BioNTech vaccine


CDC considers a history of the following to be a contraindication to vaccination with COVID-19 vaccines:

  • Severe allergic reaction (e.g., anaphylaxis) after a previous dose of the COVID-19 vaccine
  • Severe allergic reaction (e.g., anaphylaxis) to a component of the COVID-19 vaccine
  • Immediate* allergic reaction of any severity to either a previous dose of the vaccine, or known (diagnosed) allergy to a component of the vaccine

*An immediate allergic reaction happens within four hours of getting vaccinated and may include symptoms such as hives, swelling, and wheezing (respiratory distress). Generally, symptoms such as body and muscle aches, fever, headache, and redness and pain at the injection site are not indicative of a Type I Hypersensitivity Reaction and should not be considered “immediate allergic reaction.

Anaphylaxis is a life-threatening allergic reaction with onset typically within minutes to hours. Recent reports from the Centers for Disease Control (CDC) demonstrate the median interval from vaccine receipt to symptom onset was 13 minutes (range = 2–150 minutes).

Concerns related to allergic reactions based on specific ingredients follow here.  Polyethylene glycol (PEG) is an ingredient in both mRNA COVID-19 vaccines, and polysorbate 80 is an ingredient in the J&J Janssen COVID-19 vaccine.

PEG and polysorbate are structurally related, and cross-reactive hypersensitivity between these compounds may occur. People with a contraindication to one of the mRNA COVID-19 vaccines should not receive doses of either of the mRNA vaccines (Pfizer-BioNTech or Moderna). However, people with a contraindication to mRNA COVID-19 vaccines may be able to receive Janssen COVID-19 vaccine, and vice versa, provided certain measures are taken (see “precautions” below).

As a change from previous guidance, known polysorbate allergy is no longer a contraindication to mRNA vaccination; however, known polysorbate allergy is a contraindication to Janssen COVID-19 vaccine and thus, a precaution to mRNA COVID-19 vaccination.

Persons with an immediate allergic reaction to the first dose of an mRNA COVID-19 vaccine should not receive additional doses of either of the mRNA COVID-19 vaccines. In addition to screening for contraindications and precautions before administering COVID-19 vaccines, vaccine locations should follow the necessary precautions in place during and after administration:  have the necessary supplies and trained staff members available to manage anaphylaxis, implement postvaccination observation periods, immediately treat persons experiencing anaphylaxis signs and symptoms with intramuscular injection of epinephrine, and transport patients to facilities where they can receive advanced medical care. In addition, all patients should be instructed to seek immediate medical care if they develop signs or symptoms of an allergic reaction after their observation period ends and they have left the vaccination location.

Additional resources

Categories of Health Alert messages:

  • Health Alert: Conveys the highest level of importance; warrants immediate action or attention.
  • Health Advisory: Provides important information for a specific incident or situation; may not require immediate action.
  • Health Update: Provides updated information regarding an incident or situation; unlikely to require immediate action.
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