CNN-- People who have been fully vaccinated against coronavirus -- right now that means with two doses of either the Pfizer/BioNTech or Moderna vaccine -- can skip quarantine if they are exposed to someone infected with the virus, the US Centers for Disease Control and Prevention said Wednesday.
That doesn't mean they should stop taking precautions, the CDC noted in updated guidance. It's just not necessary for them to quarantine.
"Fully vaccinated persons who meet criteria will no longer be required to quarantine following an exposure to someone with COVID-19," the CDC said in updates to its webpage with guidance on vaccination.
"Vaccinated persons with an exposure to someone with suspected or confirmed COVID-19 are not required to quarantine if they meet all of the following criteria," the CDC added.
The criteria: They must be fully vaccinated -- having had both shots with at least two weeks having passed since the second shot. That's because it takes two weeks to build full immunity after the second dose of vaccine.
But the CDC says protection may wear off after three months, so people who had their last shot three months ago or more should still quarantine if they are exposed. They also should quarantine if they show symptoms, the CDC said.
"This recommendation to waive quarantine for people with vaccine-derived immunity aligns with quarantine recommendations for those with natural immunity, which eases implementation," the CDC said.
People who have been vaccinated should still watch for symptoms for 14 days after they have been exposed to someone who is infected, the CDC said.
And everyone, vaccinated or not, needs to follow all other precautions to prevent the spread of the virus, the CDC said. This is not least because it's possible even vaccinated people could harbor the virus in their noses and throats, and pass it to others.
"At this time, vaccinated persons should continue to follow current guidance to protect themselves and others, 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," the agency said.
Vaccines prevent symptomatic illness but they have not yet been shown to prevent asymptomatic illness, the CDC noted. While people with no symptoms can spread coronavirus, the CDC said, "symptomatic and pre-symptomatic transmission is thought to have a greater role in transmission than purely asymptomatic transmission."
Plus, the benefits of not unnecessarily forcing people into lockdown for two weeks may outweigh the risks of transmission in these cases, the CDC said.
"These criteria could also be applied when considering work restrictions for fully vaccinated healthcare personnel with higher-risk exposures, as a strategy to alleviate staffing shortages. Of note, exposed healthcare personnel would not be required to quarantine outside of work, the CDC said.
"As an exception to the above guidance no longer requiring quarantine for fully vaccinated persons, vaccinated inpatients and residents in healthcare settings should continue to quarantine following an exposure to someone with suspected or confirmed COVID-19; outpatients should be cared for using appropriate Transmission-Based Precautions," the CDC added.
That's because it's not clear how effective the vaccine is in people who are hospitalized.
"Although not preferred, healthcare facilities could consider waiving quarantine for vaccinated patients and residents as a strategy to mitigate critical issues (e.g., lack of space, staff, or PPE to safely care for exposed patients or residents) when other options are unsuccessful or unavailable. These decisions could be made in consultation with public health officials and infection control experts."