A health care worker holds a vial of the Johnson & Johnson COVID-19 vaccine at South Shore University Hospital in Bay Shore, N.Y., on Wednesday.

A healthcare worker holds a vial of the Johnson & Johnson Janssen Covid-19 vaccine at Northwell Health South Shore University Hospital in Bay Shore, New York, U.S., on Wednesday, March 3, 2021. President Biden said that Merck & Co. will help make Johnson & Johnson’s single-shot coronavirus vaccine, a collaboration between rivals aimed at ramping up the pace of inoculations that will help provide enough supply for every adult in the U.S. by the end of May. Photographer: Johnny Milano/Bloomberg via Getty Images