Three vaccine clinics in North Carolina have suspended administration of the Johnson & Johnson vaccine after some people had adverse reactions, including fainting.

Four people were taken to hospitals for further examination, and state and federal health officials are reviewing the matter. All four are expected to recover. One of the vaccination sites was at PNC Arena in Raleigh and two others were at clinics run by UNC Health.

The U.S. Centers for Disease Control and Prevention is examining reports of adverse reactions in multiple states, but says fainting is not uncommon. Colorado recently saw two people go to the hospital after receiving the single-dose shot.