Currently, COVID-19 vaccines by Moderna, Pfizer-BioNTech, and Janssen, a pharmaceutical company owned by Johnson & Johnson, have been approved in the United States.

After immunization, Moderna and Pfizer both recommend for patients to be monitored for 30 minutes if they have a history of an immediate allergic reaction to another vaccine or injectable therapy, and for 15 minutes after immunization for all other patients.1 Anaphylaxis is a rare, but severe side effect, with onset typically within minutes to hours. Recently, real-world data has become available regarding allergic reactions, including anaphylaxis, for Pfizer-BioNTech and Moderna.2,3

History of allergic reaction does not preclude vaccination unless the allergy is to the vaccine or its components. Currently, the only contraindications to the mRNA vaccines (Moderna and Pfizer) are a history of severe allergic reaction to its components, such as polyethylene glycol (PEG).1 A contraindication to Janssen is a known severe, allergic reaction to polysorbate.4,5 Due to structural similarities, there is some cross-reactivity between PEG and polysorbate. Appropriate risk assessment, referral to an allergist-immunologist, or a 30-minute observation period is recommended if patients with a contraindication to PEG are immunized with Jannsen’s COVID-19 vaccine, or if patients with a contraindication to polysorbate are immunized with an mRNA-based COVID-19 vaccine.

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The recent approval of Janssen’s COVID-19 vaccine serves as an alternative for patients unable to receive an mRNA COVID-19 vaccine, or is unable to complete their mRNA COVID-19 vaccine regimen due to a contraindication.5

Janssen (Johnson & Johnson)

If a patient received their first dose of an mRNA vaccine, but is unable to complete the series due to a contraindication, the patient is able to receive a single dose of Janssen COVID-19 vaccine at least 28 days after the initial mRNA dose.

Per the CDC, there are currently 3 categories for patients who have a history of allergic reactions:

To prepare for these situations, vaccination locations should:

  • Ensure necessary supplies to manage anaphylaxis are available, particularly epinephrine in prefilled syringes or autoinjectors
  • Screen recipients to identify potential contraindications or precautions
  • Implement recommended post-vaccination observation periods, either 15 minutes for patients with no previous history of allergic reactions or 30 minutes for patients with a history of allergic reactions
  • Treat suspected anaphylaxis with intramuscular epinephrine


1. Managing anaphylaxis. Centers for Disease Control and Prevention. Updated March 3, 2021. Accessed March 4, 2021.

2. Shimabukuro T, Nair N. Allergic reactions including anaphylaxis after receipt of the first dose of Pfizer-BioNTech COVID-19 vaccine. JAMA. 2021;325(8):780-781. doi:10.1001/jama.2021.0600

3. Allergic reactions including anaphylaxis after receipt of the first dose of Moderna COVID-19 Vaccine – United States, December 21, 2020 – January 10, 2021. Centers for Disease Control and Prevention. January 29, 2021. Accessed March 2, 2021.

4. Glover RE, Urquhart R, Lukawska J, Blumenthal KG. Vaccinating against COVID-19 in people who report allergies. BMJ. 2021;372:n120. doi:10.1136/bmj.n120

5. MacNeil, J. Clinical considerations for use of COVID-19 vaccines. Centers of Disease Control and Prevention. March 1, 2021. Accessed March 2, 2021.

This article originally appeared on Infectious Disease Advisor