(Reuters) -U.S. health authorities on Monday shortened the recommended time for isolation for asymptomatic Americans with COVID-19 to five days from the previous guidance of 10 days.

The Centers for Disease Control and Prevention also said the people who test positive after quarantining should follow five days of wearing a mask when around others.

Omicron accounts for 73% of U.S. coronavirus infections, the federal CDC had said last week.

Breakthrough infections are rising among the fully vaccinated population, including those who have had a third booster shot. However, Omicron appears to be causing milder symptoms in those people, some of whom have no symptoms at all.

Reducing the CDC’s 10-day quarantine recommendation would help asymptomatic people return to work or school, with proper precautions, White House medical adviser Anthony Fauci had told CNN last week.

The CDC on Monday also gave guidance for people who are unvaccinated or are more than six months out from their second mRNA dose or more than two months after the Johnson & Johnson vaccine and not yet boosted. It recommended quarantine for them for five days followed by strict mask use for an additional six days.

Individuals who have received their booster shot do not need to quarantine following an exposure should wear a mask for 10 days, the CDC said.

(Reporting by Dania Nadeem in Bengaluru; Editing by Maju Samuel)