Pfizer says tweaking its COVID-19 vaccine to better target the omicron variant is safe and boosts protection. Saturday's announcement comes just days before regulators debate whether to offer Americans updated booster shots this fall. The current COVID-19 vaccines still offer strong protection against hospitalization and death. But protection against infection has dropped markedly with the omicron variant, and now its even more transmissible relatives are spreading. Pfizer says either an omicron-targeted booster or a combination shot that mixes the original vaccine with omicron protection substantially increases protection. Rival Moderna hopes to offer a similar combination shot.