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Planning to give up the mask after vaccination? Not so fast.

With 50 million Americans immune to the coronavirus and millions more joining the ranks every day, the pressing question on many minds is: when can I throw off my mask?

It‘s a deeper question than it sounds – about getting back to normal, how quickly vaccinated Americans can hug loved ones, hang out with friends, and go to concerts, health centers. shopping and restaurants without feeling threatened by the coronavirus.

It is certain that many representatives of the State are ready. Texas lifted its mask mandate on Tuesday, along with all restrictions on business, and Mississippi quickly followed suit. Governors in both states cited declining infection rates and increasing numbers of citizens getting vaccinated.

But the pandemic is not yet over and scientists advise patience.

It seems clear that small groups of vaccinated people can get together without worrying too much about getting infected. The Centers for Disease Control and Prevention is expected to issue new guidelines shortly that will affect small gatherings of vaccinated Americans.

But when vaccinated people can ditch masks in public spaces will depend on how quickly disease rates drop and the percentage of unvaccinated people in the surrounding community.

Why? Scientists do not know whether people who are vaccinated pass the virus to those who are not vaccinated. While all Covid-19 vaccines are remarkably effective in protecting people against serious illness and death, research is unclear to what extent they prevent the virus from taking root in an immune person’s nose and then spreading. spread to others.

It is not uncommon for a vaccine to prevent serious illness but not infection. The flu, rotavirus, polio, and pertussis vaccinations are all flawed in this way.

Coronavirus vaccines “are under much more scrutiny than any of the previous vaccines,” said Neeltje van Doremalen, an expert in preclinical vaccine development at the National Institutes of Health‘s Rocky Mountain Laboratories in the Montana.

And now the coronavirus variants that bypass the immune system are changing the calculus. Some vaccines are less effective at preventing infections with certain variants and could in theory allow more virus to spread.

The research available to date on how vaccines prevent transmission is preliminary but promising. “We are convinced that there is a reduction,” said Natalie Dean, a biostatistician at the University of Florida. “We don’t know the exact magnitude, but it’s not 100%.”

Yet even an 80% drop in transmissibility could be enough for those vaccinated to throw away their masks, experts said – especially once a majority of the population is vaccinated and rates of cases, hospitalizations and deaths are falling.

But most Americans are still unvaccinated, and more than 1,500 people die every day. Given the uncertainty surrounding transmission, even those vaccinated must continue to protect others by wearing masks, experts have said.

“They should wear masks until we actually prove that vaccines prevent transmission,” said Dr Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases.

This evidence is not yet available because clinical vaccine trials were designed to test whether vaccines prevent serious illness and death, which usually reflects the impact of the virus on the lungs. Transmission, on the other hand, is driven by its growth in the nose and throat.

Initiated by the vaccine, the body’s immune fighters are expected to curb the virus soon after infection, shorten the period of infection, and reduce the amounts in the nose and throat. This should greatly reduce the chances that a vaccinated person will infect others.

Animal studies support the theory. In one study, when monkeys were immunized and then exposed to the virus, seven of eight animals had no detectable virus in the nose or lung fluid, noted Juliet Morrison, a virologist at the University of California at Riverside.

Likewise, data from a few dozen Moderna trial participants who were tested when they received their second dose suggested that the first dose reduced infection cases by about two-thirds.

Another small body of data has recently emerged from the Johnson & Johnson trial. Researchers looked for signs of infection in 3,000 participants up to 71 days after receiving the single-dose vaccine. The risk of infection in this study appeared to drop by about 74%.

“I think it’s very potent,” said Dan Barouch, a virologist at Beth Israel Medical Center in Boston, who ran one of the test sites. “These number estimates could change with more data, but the effect seems pretty strong.”

More data is expected in the coming months from Pfizer-BioNTech and Moderna.

But clinical trials can overestimate a vaccine’s potency, as the type of people who choose to participate already tend to be cautious and be advised on precautions during the trial.

Instead, some researchers track infections among people vaccinated in real settings. For example, a study in Scotland performed tests every two weeks, regardless of symptoms, on healthcare workers who had received the Pfizer-BioNTech vaccine. Investigators found that the vaccine’s effectiveness in preventing infection was 70% after one dose and 85% after the second.

Israeli researchers assessed infections in nearly 600,000 vaccinated people and attempted to trace their family contacts. Scientists have found a 46% drop in infections after the first dose and 92% after the second. (The study may have missed infections in people without symptoms.)

But to get a true assessment of transmission, researchers need to really know which immune people are infected, and then trace the spread of the virus among their contacts through DNA analysis.

“This is the ideal way to do it,” said Dr. Larry Corey, a vaccine development expert at the Fred Hutchinson Cancer Research Center in Seattle. He hopes to conduct such a study among college age students.

But what precautions should immunized people take until the results of these studies are available? At present, many experts believe that what is allowed will depend to a large extent on the number of cases in the surrounding community.

The higher the number of cases, the higher the likelihood of transmission – and the more effective vaccines need to be to stop the spread.

“If the number of cases is zero, it doesn’t matter if it’s 70% or 100%,” said Zoe McLaren, health policy expert at the University of Maryland, Baltimore County, referring to the effectiveness of vaccines. .

Mask-wearing policies will also depend on how many unvaccinated people remain in the population. Americans may need to remain cautious while vaccination rates are low. But people will be able to relax a bit as those rates rise and start to return to normal once the virus runs out of others to infect.

“A lot of people have in mind that masks are the first thing you drop,” said Dr McLaren. In fact, she said, the masks offer more freedom by allowing people to go to concerts, travel by bus or plane, or go shopping even with unvaccinated people.

Ultimately, masks are a form of civic responsibility, said Sabra Klein, an immunologist at the Johns Hopkins Bloomberg School of Public Health.

“Do you wear a mask to protect yourself from serious Covid, or do you wear a mask for public health?” Said Dr Klein. “It’s right to do your part in the community beyond yourself.