At full vaccination, the vaccines were 90% effective at preventing infections, including infections that had no symptoms. At least 14 days after first dose but before second dose, they were 80% protective, according to the agency’s Morbidity and Mortality Weekly Report published Monday. The CDC said it is the first of many planned Covid-19 vaccine effectiveness studies.
The study looked at how the vaccines protected nearly 4,000 health care workers and first responders. The volunteers in the study worked in eight locations around the country and had been observed from mid-December to…
