Covid-19 vaccine developed by the University of Oxford and AstraZeneca PLC is effective against a variant of coronavirus that is spreading rapidly in the U.S. and around the world, according to a new study, a reassuring sign for governments banking on mass vaccination to bring the pandemic to an end. The preliminary findings, published in a study online Friday that hasn’t yet been formally reviewed by other scientists, follow similarly positive results from other manufacturers.

Preliminary studies from Pfizer Inc. and Moderna Inc. found their Covid-19 shots continued to offer protection against new virus variants that have contributed to a fresh surge in cases in the U.K., Europe, South Africa and elsewhere. Vaccine makers are nevertheless readying new shots that zero in on the new variants more precisely, underlining how mutations in the virus risk morphing the year-old pandemic into a long-running cat-and-mouse game between scientists and a shifting enemy. The virus behind Covid-19 has so far been linked to almost 2.3 million deaths worldwide and more than 100 million cases.

The study published Friday looked at the AstraZeneca vaccine’s effectiveness against a new variant of coronavirus first identified in the U.K. last year.