Like most vaccines, this one may not be for everyone. The CDC says people allergic to the ingredient polyethylene glycol (PEG) or polysorbate, which is similar, should not get an mRNA COVID vaccine, and anyone who has an immediate allergic reaction to the first dose should not get the second one. People with a history of allergic reaction to a vaccine or injectable therapy for another disease should talk to their doctors, the CDC advises. It says people with food allergies do not need to avoid the vaccine.