Pfizer says it is about to seek U.S. authorization for a third dose of its COVID-19 vaccine, but U.S. health officials say a booster isn’t needed yet. The company said Thursday that another shot could dramatically boost immunity and maybe help ward off the latest worrisome coronavirus mutant. Pfizer says early data from a company trial suggests people’s antibody levels jump after they get a third dose. But the filing doesn’t mean third doses would be rolled out any time soon. Public health officials would have to decide if they’re really needed. And U.S. health officials followed Pfizer’s announcement with a statement saying they want to see more data before authorizing booster shots.