Ten to five days is the recommended isolation time for asymptomatic people, followed by five days of mouth-covering when around others, the Centers for Disease Control and Prevention (CDC) recommends, based on what is known so far about COVID-19 and its variant Omicron.
The change, the agency said, is motivated by science showing that most SARS-CoV-2 virus transmission generally occurs in the first two days before the onset of symptoms and 2 to 3 days afterward.
Thus, people who test positive should be isolated for 5 days and, if they are asymptomatic at that time, they can leave isolation and continue to wear a mask for an additional 5 days to minimize the risk of infecting others.
In addition, CDC is updating the quarantine period: for people who are unvaccinated or who are more than six months from their second dose of mRNA - or more than 2 months after the J&J vaccine - and have not yet received a booster dose, they recommend 5 days followed by strict use of masks for an additional 5 days.
Alternatively, he said, if a 5-day quarantine is not feasible, it is imperative that an exposed person wear a snug-fitting facemask at all times when around other people for 10 days after exposure.
People who have received the booster vaccine do not need to be quarantined after an exposure, but should wear a mask for 10 days after exposure. For all those exposed, best practice would also include a test for SARS-CoV-2 on day 5 after exposure.
If symptoms occur, people should be quarantined immediately until a negative test confirms that symptoms are not attributable to COVID-19.
The actions come as the Omicron variant continues to spread across the U.S. and reflect current science on when and for how long a person is highly infectious.
In a statement, the CDC said that, based on data from South Africa and the United Kingdom, the vaccine efficacy against infection with two doses of an mRNA vaccine is approximately 35 percent.
A booster dose of COVID-19 vaccine restores effectiveness to 75 percent.
The COVID-19 vaccine reduces the risk of serious illness, hospitalization, and death from COVID-19, so CDC strongly recommends COVID-19 vaccination for all persons aged 5 years and older and boosters for all persons aged 16 years and older. "Vaccination is the best way to protect ourselves and reduce the impact of COVID-19 in our communities.
"The Omicron variant is spreading rapidly and has the potential to affect all facets of our society. CDC's updated recommendations for isolation and quarantine balance what we know about the spread of the virus with the protection provided by vaccines and booster doses. These updates ensure that people can safely go about their daily lives," said CDC Director Dr. Rochelle Walensky.
He added that prevention is the best option: "get vaccinated, get a booster, wear a facemask in closed public settings in areas of substantial and high community transmission, and get tested before you meet.
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