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When the U.S. Centers for Disease Control and Prevention changed its guidelines about mask-wearing on May 13, 2021, plenty of Americans were left somewhat confused. Now anyone who is fully vaccinated can take part in indoor and outdoor activities, large or small, without wearing a mask or physical distancing.

Anthony Fauci, chief medical adviser to President Biden, said the new guideline is “ based on the evolution of the science” and “ functions as an incentive” for its almost two-thirds of Americans who aren’t yet fully vaccinated to move ahead and get the shot.

But some people cannot be vaccinated because of underlying conditions. Others with weakened immune systems, from cancer or medical treatments, might not be fully protected by their vaccinations. Children aged 12 to 15 became eligible for the Pfizer-BioNTech vaccine only on May 10, 2021. And no COVID-19 vaccines are yet authorized for the nearly 50 million children from the U.S. younger than 12.

As constraints are lifted and people start to leave their masks at home, some people worry: Can you grab COVID-19 from somebody who’s vaccinated?

Vaccines don’t always prevent disease

Researchers had expected to design safe COVID-19 vaccines that would stop at least half of the people vaccinated from getting COVID-19 symptoms.

Luckily, the vaccines have vastly outperformed expectations. By way of instance, in 6.5 million residents of Israel, aged 16 years and older, the Pfizer–BioNTech mRNA COVID-19 vaccine has been found to be 95.3% effective after both shots. Within two months, one of the 4.7 million fully vaccinated, the detectable infections dropped by 30-fold. Likewise in California and Texas, just 0.05 percent of fully vaccinated healthcare workers tested positive for COVID-19.

Vaccine developers often hope that, in addition to preventing illness, their vaccines will reach “sterilizing immunity,” where the vaccination blocks the germ from being able to enter the body in any respect. This sterilizing immunity means someone who’s vaccinated will neither catch the virus nor transmit it further. For a vaccine to work, however, it didt need to avoid the germ from infecting an immunized person.

The Salk inactivated polio vaccine, for example, does not fully stop polio virus from growing in the human gut. However, it is extremely effective at preventing the crippling disease because it triggers antibodies that prevent the virus from infecting the brain and spinal cord. Very good vaccines provide effective and durable training for your body’s immune system, so when it actually encounters the disease-causing pathogen, it’s ready to mount an optimum reaction.

When it comes to COVID-19, immunologists are still figuring out what they call the “correlates of protection,” factors that predict just how protected someone is against the coronavirus. Researchers believe that an optimum amount of “neutralizing antibodies,” the type that not only bind the virus but also prevent it from infecting, are enough to fend off repeat infections. Scientists are also still analyzing the durability of immunity that the COVID-19 vaccines are providing and where in the body it’s working.  

Can a vaccinated individual spread coronavirus?

Immunologists expect vaccines that protect against viral diseases to also reduce transmission of the virus following vaccination. But it’s actually tricky to find out for certain if vaccinated people are not spreading the germ.

COVID-19 poses a specific challenge because individuals with asymptomatic and pre-symptomatic infections can spread the illness – and inadequate contact tracing and testing imply those without symptoms are seldom detected. Some scientists estimate that the number of asymptomatic COVID-19 infections in the overall population could be 3 to 20 times greater than the number of confirmed cases. Research suggests that undocumented cases of COVID-19 in people who were asymptomatic or experienced very mild disease could be liable for up to 86% of all infections, although other research contradict the high estimates .

In one study, the CDC tested volunteer health care personnel and other front-line workers at eight U.S. places for SARS-CoV-2 infections weekly for three months, regardless of symptoms or vaccination status. The researchers found that fully immunized participants were 25 times less likely to test positive for COVID-19 than were people who were unvaccinated. Findings such as this suggest that if vaccinated individuals are so well protected from getting infected at all, they’re also not likely to spread the virus. But without contact tracing to track transmission at a larger population, it’s impossible to know whether the premise is true.

What we know for sure is that if someone does get sick with COVID-19 after vaccination, in what is called a “breakthrough infection,” symptoms will be milder. Studies have found that individuals who tested positive for COVID-19 after getting just their first vaccine dose had lower levels of virus in their bodies than unvaccinated people who tested positive. The researchers consider the decreased viral load hints that vaccinated people who do contract the virus will be less infectious because they’ll have much less virus that may be spread to others.

A preprint study that has been peer-reviewed indicates that the Moderna mRNA COVID-19 vaccine can create coronavirus-fighting Compounds in the oral and nasal fluid. Since that’s where SARS-CoV-2 makes its entrance , antibodies in the mouth and nose should block the virus from getting into the body, effectively supplying “sterilizing immunity. ” This would also imply vaccinated people probably wouldn’t spread the virus through respiratory droplets.

These pieces of evidence are promising. However, without more studies, scientists cannot yet conclude that COVID-19 vaccines really do protect against all transmission. Studies trying to immediately answer this question through contact tracing are just beginning: Researchers will track COVID-19 infections among vaccinated and unvaccinated volunteers and their close contacts.  

Protection and prevention go hand in hand

Vaccines help slow down the spread of an infectious disease by breaking the chain of infection. Those who are infected finally have fewer and fewer unprotected people to pass the virus to. This is the way a vaccine increases herd immunity – susceptible and not-yet-immunized men and women are surrounded by a “herd” of people who have become immune, because of vaccination or previous infection. But studies suggest that, for a combination of biological and social reasons, vaccination alone is unlikely to achieve herd immunity against COVID-19 and completely contain the coronavirus.

In actuality, vaccination alone can have a very long time to eradicate any disease. Even diseases that are nearly “ removed ” – such as chickenpox, measles and pertussis – can resurface with waning immunity and declining vaccine prices.

The recent epidemic of infections among the vaccinated New York Yankees shows that vaccinated individuals not only can still become infected, they may also transmit the coronavirus to close contacts. Highly tested groups, such as professional sports teams, spotlight the fact that mild, asymptomatic infections among the vaccinated in the general population might actually be more frequent than reported. A similar outbreak in airport employees in Singapore indicates that, even among the fully vaccinated, new and more infectious variants can spread quickly.

The CDC’s relaxed guidelines on masking are supposed to reassure vaccinated people that they are safe from serious illness. And they are. But the picture is less clear-cut for the unvaccinated who interact together. Until close herd immunity against COVID-19 is accomplished, and clear evidence accumulates that vaccinated people do not spread the virus, I and many epidemiologists believe it’s much better to avoid situations where there are chances to get infected. Vaccination coupled with continued masking and social distancing remains an effective way to stay safer.  

Sanjay Mishra, Project Coordinator & Staff Scientist, Vanderbilt University Medical Center, Vanderbilt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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