In guidelines updated last week, CDC said some people who are "fully vaccinated" against Covid-19 and who have been exposed to someone infected with the novel coronavirus do not have to quarantine—but only if they meet several preconditions, and only as long as they don't develop symptoms.
CDC currently recommends that most people who come in "close contact" with an individual who has a confirmed or suspected Covid-19 infection quarantine for at least 14 days.
However, in guidance updated on Feb. 10, CDC made an exception for certain people who are "fully vaccinated" against the novel coronavirus.
The agency explained that although the risk of novel coronavirus transmission from fully vaccinated people to others is still "unclear," vaccination has been shown "to prevent symptomatic Covid-19," and "symptomatic and pre-symptomatic transmission is thought to have a greater role in transmission than purely asymptomatic transmission."
Moreover, the agency said the "individual and societal benefits of avoiding unnecessary quarantine may outweigh the potential but unknown risk of transmission, and facilitate the direction of public health resources to persons at highest risk for transmitting SARS-CoV-2 to others."
As such, CDC in the guidance states that individuals "with an exposure to someone with suspected or confirmed Covid-19 are not required to quarantine if they meet all of the following criteria."
According to CDC, the criteria include being "fully vaccinated," which means individuals must have received both doses of either of the two two-shot vaccines currently authorized for use in the United States—Pfizer and BioNtech, or Moderna—or one dose of a single-shot vaccine, none of which yet have an emergency use authorization in the country.
CDC specified that for "the purposes of these quarantine criteria, considerations for accepting a vaccination series that is not FDA-authorized include whether the vaccine product has received emergency approval from the World Health Organization or authorization from a national regulatory agency."
For any vaccine, CDC added that people are not considered fully vaccinated until at least two weeks have passed since they received their final dose. According to The Hill, research indicates that people do not build up the maximum immunity until a couple weeks after their vaccination is complete.
In addition, CDC said fully vaccinated individuals may skip quarantine only if the exposure occurs within three months of their final dose—the same timeframe CDC recommends for people who have recovered from a confirmed case of Covid-19—since it remains unclear how long a vaccine's protection lasts. According to The Verge, three months is the length of time drugmakers monitored participants in vaccine trials, so that time frame could change in the future as researchers collect additional data.
CDC also urged eligible individuals to monitor their health 14 days post-exposure, noting that even fully vaccinated people should get tested and begin quarantine if they experience any symptoms.
CDC added that fully vaccinated people should continue to adhere to all other Covid-19 precautions, "including wearing a mask, staying at least 6 feet away from others, avoiding crowds, avoiding poorly ventilated spaces, covering coughs and sneezes, washing hands often, following CDC travel guidance, and following any applicable workplace or school guidance, including guidance related to personal protective equipment use or SARS-CoV-2 testing" (Wetsmen, The Verge, 2/10; Axelrod, The Hill, 2/11; CDC Vaccinations & Immunizations fact sheet, updated 2/10).