Scientists and health officials by this summer should have a better sense of what type of COVID-19 booster will be needed to deal with the next phase of the pandemic and when it should be administered, top U.S. infectious disease expert Dr. Anthony Fauci said on Friday.

The National Institutes of Health, where Fauci serves as director of the National Institute of Allergy and Infectious Diseases, is conducting clinical studies to determine if the next COVID booster should be specific to a particular variant of the coronavirus or designed to address more than one variant, known as a bivalent vaccine, ahead of the fall season, he said.

“We likely will know over the summer when we’ll be able to, and what we’ll be able to, boost people with,” Fauci said at a virtual event hosted by the National Press Club in Washington.