Those early volunteers developed what is called neutralizing antibodies in their bloodstream — molecules key to blocking infection — at levels comparable to those found in people who survived Covid-19, the research team reported in the New England Journal of Medicine.
“This is an essential building block that is needed to move forward with the trials that could actually determine whether the vaccine does protect against infection,” said Dr. Lisa Jackson of the Kaiser Permanente Washington Research Institute in Seattle, who led the study.
There’s no guarantee but the government hopes to have results around the end of the year — record-setting speed for developing a vaccine.
The vaccine requires two doses, a month apart.
There were no serious side effects, but more than half the study participants reported flu-like reactions to the shots.
The reactions aren’t uncommon with other vaccines — fatigue, headache, chills, fever, and pain at the injection site.
For three participants given the highest dose, those reactions were more severe; that dose isn’t being pursued.
Some of those reactions are similar to coronavirus symptoms but they’re temporary, lasting about a day and occur right after vaccination, researchers noted.