Merck Poised to Make J&J Vaccine, Boosting Output of Shots (2)

President Joe Biden will announce Tuesday that Merck & Co. will help make Johnson & Johnson’s single-shot Covid-19 vaccine -- a collaboration between rivals as the immunization race narrows and governments race to ramp up supply before dangerous new variants of the virus further erupt.

Assistant Press Secretary Kevin Munoz said via Twitter that Biden would announce the “historic partnership,” reported earlier by the Washington Post. White House Chief of Staff Ron Klain said in a tweet that Biden would announce the deal in afternoon remarks.

J&J’s vaccine was authorized for U.S. use on Saturday, adding a third shot...