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Revolutionary COVID infections: how long are vaccinated people contagious?


There was one parcel confusion about recent COVID-19 infections – what it means to test positive after being fully vaccinated, what is the risk of developing a “long COVID” and how those vaccinated can spread the coronavirus.

The truth is, scientists are still learning about post-vaccination infections and are still looking for answers to these questions, including how long people with breakthrough injections are contagious. But given the data available so far, most infectious disease specialists agree that it is certainly less than unvaccinated people who contract COVID-19.

Numerous studies have shown that vaccinated people who test positive generally clear the virus much faster than unvaccinated people who are infected, suggesting that people with breakthrough cases are most likely contagious for a longer period of time. short.

Some evidence suggests that vaccinated people clear the virus on average within five to six days, while unvaccinated people typically take seven to 10 days. According to infectious disease specialists, it adds up – vaccination teaches the immune system how to deal with COVID, so if you are exposed, your body can get a head start to attack the virus and eliminate it faster.

But to get a clear idea of ​​how long people with breakthrough infections are contagious, we need real data on transmission events, of which we don’t have a lot. “We don’t really know the degree to which vaccinees have spread, because you really need to do a good contract research study.” Monique Gandhi, an infectious disease specialist at the University of California at San Francisco, told HuffPost.

How we determine the infectivity of COVID

Scientists assessed infectivity by looking at the amount of virus found in people’s noses. A person’s nose is swabbed with a PCR test kit, which tells us two things: whether the virus is present and, if so, an estimate of how much virus is present (i.e. the load viral). But what the PCR doesn’t tell us is how contagious this virus is. Usually with other diseases, when we want to measure infectivity, we grow (in other words, examine) the virus from a person’s nose to see if it is alive or not.

“A PCR only amplifies the sequence of the virus but does not say in any way whether it is alive or in good health and can pass from one person to another” Gandhi said.

According to Gandhi, the best way to understand how contagious vaccinated people infected with emerging infections are would be to trace contacts. With tracing studies, you can actually see if and when vaccinated people pass the virus on to others.

But we don’t yet have many contract research studies examining revolutionary cases and transmission events. Most of the information we have about the contagiousness of breakthrough cases comes from laboratory studies and PCR tests which usually only tell us if there is a virus in a person’s body, not if it is. infectious and for how long it could be infectious.

Luis Alvarez via Getty Images

People vaccinated, on average, are generally less contagious and for a shorter duration.

Vaccinated people seem less contagious

So while the real answer to the duration of contagiousness for people with breakthrough infections is “we don’t really know yet,” scientists have learned a few things.

A study from Singapore found that although the viral loads of vaccinated and unvaccinated people had similar peaks at the onset of infection, the viral loads of vaccinated people fell much faster than those of unvaccinated people. The viral load in those vaccinated dropped to levels that are generally thought to be non-infectious about six days after the onset of illness. Meanwhile, the viral load in unvaccinated people dropped to this same level after 10 days.

A Harvard Study also found that vaccinated people seemed to clear the virus in 5.5 days compared to unvaccinated people who cleared it in 7.5 days. Another report from the University of Illinois found more of the same. Vaccinated people “clear it more quickly from the upper respiratory tract, so they are less contagious,” said Adam ratner, the Director of Pediatric Infectious Diseases and member of the Vaccination Center at New York University Langone Health.

Researchers from the Netherlands went further and looked at respiratory samples taken from vaccinated people with breakthrough infections and found that the virus in their noses was less likely to be infectious than unvaccinated people who contracted COVID. Nevertheless, an infectious virus was detected in 68% of vaccinated participants (compared to 85% of unvaccinated participants).

The Singapore study also found that vaccinated people were more likely to be asymptomatic, and those who showed symptoms of breakthrough infections generally had fewer symptoms than unvaccinated people with COVID. This is another reason why people who are vaccinated are likely to be less contagious – if you cough less, you won’t generate as much aerosolized virus as someone who coughs and blows his nose a lot.

“People who have the worst symptoms – who cough more and have more snot flowing from their nose – are more contagious on that basis alone,” Ratner said.

While it is generally accepted that people who are vaccinated, on average, are less contagious overall and for a shorter period of time, it is still not clear to what extent people are contagious at any given time during their infection. It is widely believed that some people vaccinated with COVID will be very contagious while those who are asymptomatic probably won’t spread a lot of viruses at all.

“If you are symptomatic and have a breakthrough, I think you are able to transmit,” Gandhi said. Ultimately, how long a given person is contagious seems to depend on various factors, such as their immune response and the severity of symptoms.

What is the best course of action?

The Centers for Disease Control and Prevention still advises anyone who tests positive for COVID-19, whether vaccinated or symptomatic, to self-isolate for 10 days. Ratner said that until there is more concrete data on how long people with breakthrough cases are shedding the virus, the safest thing is to stick to the 10-day isolation rule.

A growing number of infectious disease specialists are recommending that vaccinated people avoid having additional PCR tests after symptoms have passed. PCR tests are so sensitive that they can detect super low viral loads (it probably wouldn’t be contagious) and pieces of potentially dead virus. This is different from advice for determining if you have an infection at the onset of symptoms or after exposure; experts say a PCR is still the gold standard out there.

Once you’ve recovered from a groundbreaking disease, Gandhi suggested skipping the PCR test and switching to a rapid antigen test instead. Rapid antigen tests are not very good at detecting small traces of the virus, but are useful at identifying high viral loads that indicate a person is quite contagious.

“Wait for the symptoms to go away, take a quick antigen test – and when it’s negative, you can come out again,” Gandhi said.

Experts are still learning about COVID-19. The information in this story is what was known or available at the time of publication, but directions may change as scientists find out more about the virus. Please consult the Centers for Disease Control and Prevention for the most recent recommendations.

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