People infected with COVID-19 do not necessarily have immunity to reinfection for three months, the CDC said late Friday night, trying to squelch speculation the agency had inadvertently stimulated.
While people can continue to test positive for SARS-CoV-2 for up to three months after diagnosis and not be infectious to others, that does not imply that infection confers immunity for that period, the agency said.
The confusion stemmed from an August 3 update to CDC's isolation guidance, which stated:
Who needs to quarantine?
People who have 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 COVID-19 do not need to quarantine or get tested again for up to 3 months as long as they do not develop symptoms again. People who develop symptoms again within 3 months of their first bout of COVID-19 may need to be tested again if there is no other cause identified for their symptoms.
These statements could be read as suggesting that those recovering from COVID-19 will likely be safe from reinfection for three months even with close exposure to infected people. Media reports took this as a tacit acknowledgment of immunity from the agency.
Friday's CDC statement chided the media for misinterpreting its guidance, which was about retesting, not immunity.
"The latest data simply suggests that retesting someone in the 3 months following initial infection is not necessary unless that person is exhibiting the symptoms of COVID-19 and the symptoms cannot be associated with another illness," the agency said.
In fact, the CDC went so far as to update its update, which now says explicitly, "We do not know if someone can be re-infected with COVID-19." The agency added that people who were previously infected may continue to have "low levels of virus in their body for up to 3 months," which could explain positive test results even if they recovered from the virus.
Based on more than 15 international and U.S.-based studies examining various aspects of infection, the agency concluded the duration of infection in most people is no longer than 10 days following symptom onset, and no more than 20 days in people with severe illness or those who are "severely immunocompromised," the agency said.
The CDC added there are no confirmed reports of reinfection within 3 months of initial infection. The guidance still recommends that if those recovering from the virus come into contact with a positive case and have new symptoms, they should isolate themselves, contact their healthcare provider and possibly be retested.
Everyone, including those recovering from COVID-19, should continue to follow the recommended non-pharmaceutical interventions, including social distancing, wearing a face mask in public, and washing their hands, the agency said.
In the statement, the CDC reiterated that people who test positive for COVID-19 should isolate for at least 10 days after symptom onset and until 24 hours after their fever subsides without the use of fever-reducing medications.