The study was based on 186 individuals which whom had at last one allergic reaction, such as flushing, hives, or shortness of breath, within 4 hours after receiving their first dose.
159 people received the second dose. Of this 159, 47 were given antihistamine medications before the shot. All individuals, including 19 people who experienced anaphylaxis after the first dose, tolerated the second dose. Thirty-two experienced allergy symptoms after their second dose that were self-limited and resolved with antihistamines.
Antihistamine treatment can help prevent allergy symptoms like hives, shortness of breath, and flushing. Anyone who developed a reaction after their first dose plus those with a history of reactions to vaccines should work with an allergy specialist to get fully vaccinated.