Britain to test mixing and matching of COVID-19 vaccines

British scientists are going to test whether COVID-19 vaccines can be mixed and matched. The vaccines that are rolling out now require two doses, weeks apart, and they should be the same kind. In the study starting Thursday, participants will get one shot of the AstraZeneca vaccine followed by a Pfizer dose, or vice versa. The vaccines use different technologies and it’s unclear whether mixing them might work. But British officials say that, if successful, the study could allow for more flexible policies and help deal with vaccine shortages. Researchers are hoping to enroll 800 volunteers.