Vaccinations and booster shots continue to be the best defense against the coronavirus for the U.S., even with the spread of the new omicron variant, which now has been reported in at least 15 states, health officials said Sunday. Vaccines developed to fight the original COVID-19 strain have offered good protection against the delta variant, the dominant strain in the U.S., said Dr. Anthony Fauci … He believes they will help with omicron, especially for those who also get a booster shot.