BACKGROUND AND PURPOSE:

• As of January 10, 2021, approximately 4-million first doses of the Moderna COVID-19 vaccine have been administered in the U.S.
  • Rare cases of anaphylaxis and other allergic reactions have been reported with the Pfizer-BioNTech COVID-19 vaccine, another mRNA-based vaccine
• The CDC COVID-19 response team (MMWR, 2021) reported on cases of allergic reactions, including anaphylaxis, associated with first-dose vaccination of the Moderna vaccine

METHODS:

• Data sources
  • Vaccine Adverse Event Reporting System (VAERS)

RESULTS:

• 1266 adverse events
  • 108 case reports identified for further review for possible cases of allergic reaction, including anaphylaxis

Anaphylaxis

• Anaphylaxis cases: 10 (all women)
• Anaphylaxis rate: 2.5 cases per million doses
• Median age: 47 years (range 31 to 63 years)
• Cases with history of allergies or allergic reactions: 9
  • 5 had a history of anaphylaxis
• Median interval from vaccine receipt to symptom onset: 7.5 minutes (range 1 to 45 minutes) | 9 cases within 15 minutes
• All patients received IM epinephrine and 6 hospitalized
  • 5 ICU | 4 intubated
• Follow-up (available in 8 cases) 
  • All recovered or discharged home

Other allergic reactions and adverse events

• Other non-anaphylaxis allergic reactions
  • 43 cases within 0 to 1 day risk window
  • 60% (26/43) classified as nonserious  
  • Commonly reported symptoms: Pruritus | Rash | Itchy sensations in the mouth and throat | Sensations of throat closure | Respiratory symptoms

CONCLUSION:

• Anaphylaxis following the first dose of the Moderna vaccine is very rare, and occurred within 45 minutes of receipt with a median time of 7.5 minutes
• The CDC recommends that

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 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

Learn More – Primary Sources:

Allergic Reactions Including Anaphylaxis After Receipt of the First Dose of Moderna COVID-19 Vaccine — United States, December 21, 2020–January 10, 2021

Related ObG Topics:

How Common are Anaphylaxis and Allergic Reactions Following Pfizer-BioNTech COVID-19 Vaccination?

The Moderna Vaccine: Study Results Presented to ACIP CDC Committee