mind, could have been mitigated or decreased substantially. >> reporter: and a cdc study recently followed health care workers, and found that the pfizer and moderna vaccines were 90% effective at preventing both symptomatic and asymptomatic disease. they appeared to be 80% effective two weeks after one dose. the study also suggests that it appears the vaccines slow the spread of the virus. doctors are reminding patients that you need both doses to be considered fully vaccinated and have max protection. david? >> encouraging news. after one dose, but still get that second dose. eva, thank you. next, a report on the origins of covid-19 in wuhan, china, is due tomorrow. reportedly concluding that the virus most likely spread directly from bats to another animal and then to humans. the 100-plus page report from the world health organization and china also finding it's extremely unlikely the virus escaped from a wuhan lab. china's dey in allowing outside experts in has cast a shadow over the investigation.