The U.K. became the first country to approve Moderna Inc.’s Omicron-targeting Covid-19 vaccine as a booster shot, paving the way for the variant shot to play a role in a planned fall vaccination campaign to shore up immune defenses against the virus.

The so-called bivalent vaccine is directed against both the original strain of SARS-CoV-2, the virus that causes Covid-19, and the first Omicron variant, also known as BA.1, which drove large waves of infection over the winter.