New data support 5 days of isolation for COVID-19 infections plus 5 days of masking — study

A new study supports current guidelines that call for a five-day isolation period for COVID-19 infections followed by five days of strict masking to help prevent transmission from cases that remain culture positive, researchers said.

Boston University School of Medicine researchers collected daily nasal swabs for at least 10 days from 92 vaccinated college students and staff infected with the Delta or Omicron variants of the coronavirus for analysis with PCR and with the kind of rapid-antigen tests that are available for home use.

Among these young and otherwise healthy adults, only 17% still tested positive after five days, and no one was infectious beyond 12 days after symptom onset, the researchers reported in Clinical Infectious Diseases.

The results were similar regardless of variant or vaccine booster status, and negative rapid antigen tests were very reliable, according to the report.

While rapid antigen testing "may provide reassurance of lack of infectiousness... a full 10 days is necessary to prevent transmission from the 17 percent of individuals who remain culture positive after isolation," study leader Dr. Tara Bouton said in a statement. -- Reuters