The U.S. Food and Drug Administration (FDA) is expected to allow the mixing and matching of COVID-19 vaccine booster doses this week, according to reports.

The forthcoming announcement by the agency is anticipated as the campaign for additional shots continues and as more Americans head back for a third jab.

The Associated Press reported on Tuesday – citing an anonymous U.S. health official familiar with the matter – that the news would likely be put out alongside the authorization for boosters of the Moderna and Johnson & Johnson shots, though the FDA was still predicted to say that using the same brand for a booster was the preferable option and especially for mRNA vaccines from Pfizer and Moderna.

The FDA declined to comment.