The Centers for Disease Control and Prevention released three studies on Wednesday that federal officials said provided evidence that booster shots of the Pfizer-BioNTech and Moderna coronavirus vaccines would be needed by all Americans in the coming months.

But some experts said the new research did not support the decision to recommend booster shots for all Americans.

Taken together, the studies show that although the vaccines remain highly effective against hospitalizations, the bulwark they provide against infection with the virus has weakened in the past few months.