within a week. each variant has its own little shop of horrors, and in the case of the omicron variant, that s what this is, that one-two punch of so many people getting infected and knocking out a substantial segment of our healthcare workforce at the same time. reporter: peter hotez is a virologist at houston s baylor college of medicine and reommends a fourth shot for healthcare workers and those who are imnocompromised. the level of protective immunity after the third immunization against the omicron variant wans, declines pretty rapidly. reporter: massachusetts is one of several states activating the national guard to support hospitals as omicron spreads. spreads. you think that people should reconsider holiday plans? i think people should take a hard look at them and really think about their individual situations with their families. reporter: and tonight, another weapon in the fight against covid. the f.d.a. is reportedly expected to approve treatment