Roughly 58% of people in the U.S. now have antibodies from previous Covid infection, demonstrating how widespread the virus was during the winter omicron surge.
The CDC analyzed about 74,000 blood samples every month from September through January from a national commercial lab network. The sample size decreased to about 46,000 blood samples in February. The CDC tested the samples for a specific type of antibody that is produced in response to Covid infection, not from vaccination.
"Those who have detectable antibody from prior infection, we still continue to encourage them to get vaccinated," Walensky told reporters during a call."We don't know when that infection was. We don't know whether that protection has waned. We don't know as much about that level of protection than we do about the protection we get from both vaccines and boosters."