People who have recovered from COVID-19 can safely interact with others for three months, according to a recent update from the Centers for Disease Control and Prevention — suggesting that immunity to the virus may last at least that long.
The recent change is part of the agency's guidance on quarantining. It states that people should quarantine if they've been in close contact with someone who has COVID-19, "excluding people who have had COVID-19 within the past 3 months." People who have tested positive for the virus don't need to be tested again for up to three months, as long as they don't develop symptoms again.
The CDC previously acknowledged that people who have recovered from COVID-19 can test positive for the virus for up to three months, though these positive results don't mean that a person is still sick. Instead, the test may be picking up fragments of the virus's genetic code. Dr. Brett Giroir, the undersecretary of health who leads coronavirus testing for the White House, has advised people against being tested again after they recover.
However, the update goes one step further, suggesting that people who have recovered are protected from getting sick again for at least three months.
The guidance is based on studies that found that, after three months, there was no evidence of people getting re-infected after recovering, a CDC official said. Longer-term studies are needed to determine how long protection might last, and it's still too soon to say to whether a person who has had COVID-19 and recovered is immune.
The update, which was posted on the CDC's website on Aug. 3, is consistent with CDC's earlier guidance not to retest patients within 90 days of an initial infection, Dr. Annie Luetkemeyer, a professor of medicine at the University of California, San Francisco, said. Although some doctors and patients have raised concerns about the possibility of being reinfected with coronavirus, there have been no confirmed reports of reinfection.
Dr. Joshua Barocas, an assistant professor of medicine at the Boston University School of Medicine, said the CDC's update "aligns with the idea that it is unlikely that people can be infected within a three month time frame."
"Of course, unlikely doesn't mean it is impossible to get reinfected," Barocas said, adding that people should be cautious and quarantine "unless it's a crystal clear case."
He noted that the CDC's guidance shouldn't be over-interpreted "an an indication that we have or could soon achieve herd immunity."
"We are not there and we shouldn't rely on that as it will cause a significant amount of mortality."