Guidelines on quarantine after COVID-19 vaccination: Protections, Recommendations
Photo: Andalou Agency

Fully vaccinated people can now skip quarantine even if they've been exposed to Covid-19, according to new guidelines from the US Centers for Disease Control and Prevention. The new guidance only applies if it has been at least two weeks since your final dose, no more than three months since that dose, and provided you don't develop symptoms. But at the same time, the agency also acknowledges there's a lot of researchers don't know about how vaccines impact transmission. Plus that doesn't mean you can stop wearing a mask, keeping your distance from others, and following other CDC guidance. You're also not exempt from testing requirements for those returning from abroad.

While the guidelines imply that vaccinated people may be less likely to transmit the virus, the CDC makes clear that vaccine trials have largely focused on preventing symptomatic cases of Covid-19. That doesn't mean people can't catch the virus and spread it asymptomatically. But that's significantly harder to measure, experts say.

Measuring transmission indirectly

Directly measuring the transmission of Covid-19 is difficult, so researchers use proxies to estimate how likely a person might be to transmit the virus. One potential proxy is viral load - how much virus people have to circulate in their bodies. Research has shown that people with lower viral loads are less likely to transmit the virus.

A recent study in Israel found that people who had been infected 12 to 28 days after their first dose of the Pfizer vaccine had viral loads that were four-fold lower than if they were infected in the first 12 days. While the study had not been peer-reviewed and doesn't include data after the second dose, Ranney said the findings were "really exciting. It suggests that you're less likely to pass it on to others even after the first weeks -- even before you've been fully immunized," she said.

Another study on the AstraZeneca vaccine also suggested that it could affect the transmission, but it did so using a different measure. The researchers collected nasal swabs from trial participants in the UK every week and found that the rate of positive tests fell by half after two doses of the vaccine. Neither of these studies measured transmission directly -- for example, by tracing contacts of study volunteers to see whether they became infected. But they give a positive sign of what experts have suspected for some time, based on experiences with vaccines for other diseases, said CNN.

"It assumes, I think, that the vaccines are also interrupting asymptomatic transmission" and preventing the virus from replicating in people's noses and mouths, said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. "I think that's probably true," he said, adding, "I don't know that we have all the i's dotted and the t's crossed."

Guidelines on quarantine after COVID-19 vaccination: Protections, Recommendations
Photo: France24

What are the protections?

Currently, it’s unknown how effective the COVID-19 vaccines are at preventing transmission of the virus. But their effectiveness at preventing disease has proven to be significant.

“The data from the studies that were done show that … for the Pfizer vaccine, people are 95 percent protected 7 days after their second dose, and for the Moderna vaccine people are 94 percent protected 14 days after their second dose,” Maldonado said.

Although the information on transmission effectiveness is limited, preliminary data is promising. “We know that from the Moderna study they did swabs on asymptomatic vaccines at the time of the second dose, so 4 weeks after the first dose, and there was a 63 percent reduction in positive swabs in the vaccine group compared to the control. In some AstraZeneca studies, they found very similar decreases,” Dr. Dean Blumberg, chief of pediatric infectious diseases at the University of California Davis, told Healthline.

“We’ve been waiting for this ever since the vaccines were made available,” he said. “We always envisioned that vaccines would result in us returning to some sort of sense of normality eventually without having to mask and without having to social distance, so I think this is one step in the right direction.”

Limited data, limited recommendations

More studies that test vaccinated people regularly for Covid-19 will give doctors a better understanding of how vaccines impact transmissibility, and for how long, Ranney said. That's partly why the recommendation only applies up to three months -- because the CDC and vaccine makers don't have much data going out any longer than that after people have been vaccinated. "Certainly vaccines will last more than three months," Hotez said.

DC made similar updates to their quarantine guidelines back in August, when it said people who have recovered from Covid-19 in the past three months do not have to quarantine or get tested again as long as they do not develop new symptoms. According to the agency, "available evidence suggests that most recovered individuals would have a degree of immunity for at least 3 months," and reinfection appears to be uncommon during that time. But the risk is not zero. Still, despite the uncertainties, Hotez and Ranney said the new guidance is a step in the right direction. "In some ways, it's a welcome recommendation because, at some point, we've got to start working towards normalcy and opening up the country," Hotez said.

Guidelines on quarantine after COVID-19 vaccination: Protections, Recommendations
Photo: USA News

Still follow safety protocols

Experts emphasize that those who are vaccinated still have a responsibility to the general public to continue to abide by COVID-19 guidelines. “The vaccines are not a ‘get out of jail free’ card. That’s the only downside of the new recommendation. It could, in some minds, cause more ambiguity and confusion,” Dr. Scott A. Kaiser, a primary care physician, and geriatrician at Providence Saint John’s Health Center in California, told Healthline.

In the updated guidance, the CDC states that “at this time, vaccinated persons should continue to follow current guidanceTrusted Source 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 guidanceTrusted Source, and following any applicable workplace or school guidance, including guidance related to personal protective equipment use or SARS-CoV-2 testing.” These safety measures, Kaiser argues, are unlikely to change even with more people receiving vaccinations.

“We need to continue to do all of these things to reduce the transmission, reduce the spread of the virus. The vaccines are one tool in our toolkit, but all of these things are effective at reducing transmission of the virus and now it’s more important than ever to be doing that because there are… variants and strains that are resulting in more severe cases,” he added.

Frequently asked questions

Question: Did the CDC say fully vaccinated people do not need to quarantine after possible or confirmed exposure to COVID-19?

Answer: Yes, but only if you fit three criteria:

  • It's been at least two weeks since your final vaccine dose,
  • It's been within three months or 90 days of your final dose,
  • And you are showing no symptoms

The CDC advises that anyone who does not meet those three criteria should follow the CDC's quarantine guidance of staying home and away from others for 14 days. "We’re not suggesting someone who is vaccinated cannot spread COVID-19 within the first 90 days of being fully vaccinated, nor are we suggesting that expected protection from COVID-19 vaccines wears off after 90 days."

Question: Is it OK if you don’t get a second COVID-19 vaccine dose on time?

Answer: Health experts stress the importance of getting the second COVID-19 vaccine dose on time, but it is OK if you have to wait longer before getting it. The Centers for Disease Control and Prevention (CDC) recommends health care providers give the second dose of the Moderna vaccine four weeks after the first shot. Doses of the Pfizer-BioNTech vaccine are supposed to be given three weeks apart, according to the CDC.

“The [COVID-19 vaccine] studies were actually done with a three- or four-day window,” explained Corey. “So, when it says day 21, it could be 17. I would not get [the second dose] on day 15 or 16, but you know, a couple of days here or there… it’s not going to make a difference.”

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