The Centers for Disease Control and Prevention has stated that severe allergic reactions to Modernas COVID-19 vaccine seem to be rare.

A CDC report states that only 10 individuals developed severe allergic reactions (anaphylaxis) among over 4 million people who were administered a first dose of the Moderna COVID-19 vaccine as of January 10. This amounts to a rate of 2.5 cases per million doses. In a previous report, the CDC had revealed that with the Pfizer/BioNTech vaccine against COVID-19, 11.1 individuals out of every million vaccinated had a severe allergic reaction. The rate of severe allergic reaction with the flu vaccine, in comparison, stands at 1.3 per million doses… (CNN, January 22, 2021)