Britain to test mixing, matching COVID vaccines

British scientists are starting a study Thursday to find out if it’s OK to mix and match COVID-19 vaccines.

The vaccines being rolled out now require two doses, and people are supposed to get two shots of the same kind, weeks apart.

Guidelines in Britain and the U.S. say the vaccines aren’t interchangeable, but can be mixed if the same kind isn’t available for the second dose or if it’s not known what was given for the first shot.

Participants in the government-funded study will get one shot of the AstraZeneca vaccine followed by a dose from Pfizer, or vice versa.

“This study will give us greater insight into how we can use vaccines to stay on top of this nasty disease,” said Jonathan Van Tam, the U.K.’s deputy chief medical officer.

He said that given the challenges of immunizing millions of people amid a global vaccine shortage, there would be advantages to having data that could support more “flexible” immunization campaigns.