People who have received the full course of Covid-19 vaccines can skip the standard 14-day quarantine after exposure to someone with the infection as long as they remain asymptomatic, US public health officials advised.
The Centers for Disease Control and Prevention (CDC) said late on Wednesday the vaccines have been shown to prevent symptomatic Covid-19, thought to play a greater role in the transmission of the virus than asymptomatic disease.
"Individual and societal benefits of avoiding unnecessary quarantine may outweigh the potential but unknown risk of transmission (among vaccinated individuals)," the CDC said.
Meanwhile, the nation's top infectious disease expert, Anthony Fauci, said he expects the pace of vaccination to dramatically increase by April, he told NBC's Today show.
"By the time we get to April," it will be "open season, namely virtually everybody and anybody in any category could start to get vaccinated".
The CDC recommends vaccinated people still wear masks, practice social distancing, and avoid poorly ventilated spaces and crowds. That is because there is still limited information on whether the vaccine can prevent transmission and how long it confers protection against the virus.
As more study data on transmission is released, and as more people are vaccinated, these recommendations could change.
The agency has laid down strict criteria for people who would no longer have to quarantine after the vaccinations, including having received both doses of a two-dose vaccine.
People who choose not to quarantine should do so only if they received their last dose within three months, and should only avoid quarantine 14 days after their last shot, the time it takes to develop immunity, CDC said.
Fully vaccinated persons who do not quarantine should still watch for symptoms for 14 days following an exposure.
Further, the agency still recommends in-patients and residents of long-term care homes be quarantined after an exposure to Covid-19, because there is less data on the effectiveness of the vaccine in this population and because of a high-risk of disease and death.
Two-dose vaccines from Pfizer Inc and Moderna Inc have been authorized for emergency use in the United States. Johnson & Johnson applied for a US authorization of its single-dose shot last week.
The CDC said its loosened quarantine recommendations only apply to people vaccinated with these two products, since it has not systematically evaluated vaccines available in other countries.