A health-care provider who was vaccinated Tuesday in Alaska is under observation in the hospital after experiencing an allergic reaction to Pfizer’s vaccine. Although the individual didn’t have any known drug allergies, it’s unclear if they have food or other allergies, according to The New York Times. The person’s reaction was similar to that of two health workers in Britain who were vaccinated last week. They were hospitalized but have now both recovered. Pfizer’s vaccine trials, which involved more than 40,000 people, didn’t unearth any serious side effects, and the Centers for Disease Control and Prevention has said that people with serious allergies can be vaccinated as long as they’re monitored for symptoms for a half an hour afterwards.