Quarantine is typically recommended for healthy people who have been exposed to the virus. During quarantine, people are asked to isolate from others for one to two weeks to see whether they develop symptoms of Covid-19. By not exposing others, quarantining can help stop the spread of the disease.
In the updated guidance, the CDC said such quarantining is not necessary for fully vaccinated people within three months of having received their last doses as long as they do not develop any symptoms. “Fully vaccinated” means that at least two weeks have passed since a person has received the second dose of a two-dose vaccine or one dose of a single-dose vaccine.
Other recommendations remain in place for fully vaccinated people. They include wearing masks, social distancing and avoiding crowds and poorly ventilated spaces.
The guidance says the risk that fully vaccinated people could spread the coronavirus, to others is “still uncertain.” However, “vaccination has been demonstrated to prevent symptomatic Covid-19; symptomatic and pre-symptomatic transmission is thought to have a greater role in transmission than purely asymptomatic transmission,” according to the CDC.
The CDC already recommends that people who have had Covid-19 and recovered do not need to quarantine for 90 days after the illness, if newly exposed to someone who is infected; the new guidance for vaccinated people aligns with the earlier recommendations.
A spokesperson for the CDC declined to comment about the updated guidance.
The guidance “makes sense,” said Dr. Peter Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine in Houston and co-director of the Center for Vaccine Development at Texas Children’s Hospital, although he said he was curious about what evidence the CDC was using.
Early data from AstraZeneca and Moderna’s Phase 3 clinical trials have suggested that vaccines may slow transmission of the virus, although more work is needed to confirm the findings.
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Saskia Popescu, an epidemiologist and infection preventionist at George Mason University in Virginia, said the new guidance “reiterates that there is confidence in protection for those 90 days following vaccination, which is similar to the robust immunity after infection.”
Guidance “will likely evolve as we get a better understanding of vaccine-derived immunity,” particularly for those outside the three-month post-vaccination period, Popescu said.