People who've recovered from coronavirus may be protected from the virus for at least three months, The Centers for Disease Control and Prevention suggested Friday.
In updated guidance on its website, the CDC said that you should quarantine if you've had close contact with anyone diagnosed with COVID-19—unless you've had COVID-19 within the last three months.
The guidance suggests that people who've recovered from the virus may not be able to spread it to others for at least three months.
The three-month figure has come into play before in public health advice about the illness: Officials have previously said that people who've tested positive for coronavirus don't need to be retested within that time period.
That advice still stands. "People who have tested positive for Covid-19 do not need to quarantine or get tested again for up to three months as long as they do not develop symptoms again," the current guidance says. "People who develop symptoms again within three months of their first bout of Covid-19 may need to be tested again if there is no other cause identified for their symptoms."
The CDC's update "aligns with the idea that it is unlikely that people can be infected within a three-month time frame," Dr. Joshua Barocas, an assistant professor of medicine at the Boston University School of Medicine, told NBC News on Friday. "Of course, 'unlikely' doesn't mean it is impossible to get reinfected."
Not a sign of herd immunity
He added that people should quarantine "unless it's a crystal-clear case" and warned that the new guidance should not be interpreted as "an indication that we have or could soon achieve herd immunity."
What length of immunity, if any, infection with the coronavirus confers has been a hot topic since the pandemic's earliest days. Doctors say that other respiratory coronaviruses—such as those that cause SARS and MERS—make patients immune from reinfection for about a year.
Some isolated cases of people being reinfected with coronavirus have been reported, but not on a widespread basis. Medical experts are somewhat skeptical about those few cases, saying they are more likely a resurfacing of symptoms from the patients' initial infection.
How long you should quarantine
If you've tested positive for coronavirus, the CDC's current guidance is that you can safely end home isolation and return to work or school if three conditions are met: it's been 10 days after the start of symptoms; if you've not had a fever for at least 24 hours; and if your other symptoms of COVID-19 are improving. If you've had no symptoms, you can be around other people 10 days after first testing positive for COVID-19.
As for yourself, do everything you can to prevent getting—and spreading—COVID-19 in the first place: Mask, get tested if you think you have coronavirus, avoid crowds (and bars, and house parties), practice social distancing, only run essential errands, wash your hands regularly, disinfect frequently touched surfaces, and to get through this pandemic at your healthiest, don't miss these 37 Places You're Most Likely to Catch Coronavirus.