due to covid issues and schools like harvard university moving graduate and professional schools to online classes for the first three weeks of january. covid striking governor larry hogan and members of congress with elizabeth warren, new jersey senator corey booker, and colorado congressman jason crow, all testing positive for the virus. health workers and government officials increasingly focused on boosters. we see those a are vaccinated, who have received their booster, aren t coming in at the same rates. reporter: moderna showing that its half dose booster shot increased antibody levels against omicron, noticing a larger size dose helped even more. right now, you need that third dose. i wish we on stop calling it a booster. it s a three-dose vaccine. reporter: basic mitigation measures like mask kg help slow