People who have been fully vaccinated against Covid-19 do not need to be quarantined if they are exposed to the coronavirus, the Center for Disease Control and Prevention said on Wednesday in an updated guide on its website.
Quarantine is generally recommended for healthy people who have been exposed to the virus. During quarantine, people are asked to isolate themselves from others for one to two weeks to see if they develop Covid-19 symptoms. By not exposing others, quarantine can help prevent the disease from spreading.
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In the updated guidance, the CDC said that such a quarantine is not necessary for people fully vaccinated 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 received the second dose of a two-dose vaccine or one dose of a single-dose vaccine.
Other recommendations remain in effect for people who are fully vaccinated. They include wearing masks, social distance and avoiding crowds and poorly ventilated spaces.
The guidance says that the risk that fully vaccinated people may spread the coronavirus to others “is still uncertain”. However, “vaccination has been shown to prevent symptomatic Covid-19; symptomatic and pre-symptomatic transmission is believed to play 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 be quarantined for 90 days after the disease, if they have recently been exposed to someone infected; the new orientation for vaccinated persons is in line with previous recommendations.
A CDC spokesman declined to comment on the updated guidance.
The guidance “makes sense,” said Dr. Peter Hotez, dean of the National School of Tropical Medicine at 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 suggested that vaccines may delay transmission of the virus, although more work is needed to confirm the results.
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Saskia Popescu, an epidemiologist and infection preventer at George Mason University in Virginia, said the new guideline “reiterates that there is confidence in protection for the 90 days after vaccination, which is similar to robust immunity after infection.”
The guidance “will likely evolve as we gain a better understanding of vaccine-derived immunity,” particularly for those outside the three-month post-vaccination period, Popescu said.
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Akshay Syal and Erika Edwards contributed.