Behind the masks, a mystery: How often do vaccinees spread the virus?

Director of the Centers for Disease Control and Prevention, Dr. According to Rochelle Valensky, the recommendation to vaccinate people with their masks in some parts of the country was based largely on a disturbing finding.

New research has shown that vaccinated people are infected with delta version Responding to questions from The New York Times, he said in an email that there is a tremendous amount of virus in the nose and throat.

The finding contrasts with what scientists had seen in people infected with previous versions of the virus, which were mostly unable to infect others.

That conclusion dealt a massive blow to Americans: People with so-called breakthrough infections — cases that occur despite full vaccination — can be just as contagious as people without the delta variant, even if they don’t have any symptoms.

This means fully immunized people with young children, aging parents, or friends and family with weakened immune systems will need to renew vigilance, especially in communities with high transmission. Vaccinated Americans may require everyone in their class to wear a mask, not only for their own safety.

As of Thursday, the United States is reporting an average of 67,000 new cases per day. If vaccinated people are transmitting the delta variant, they may have contributed to the increase – although possibly to a much lesser degree than the unvaccinated.

The CDC has yet to publish its data, which frustrates experts who want to understand the basis of the change of heart on the mask. Four scientists familiar with the research said it was compelling and justified the CDC’s advice that vaccinated people wear masks again in public indoor spaces.

The research was carried out by people outside the CDC, the scientists said, and the agency is working rapidly to analyze and publish the results. An official said the agency expects to publish the research on Friday.

some research May be partly related to an outbreak in Provincetown, Mass., where 882 cases have been reported till Thursday in the Fourth of July celebration. About three-quarters of those people were fully vaccinated.

The agency has also tracked data from the COVID-19 Sports and Society Workgroup, a coalition of professional sports leagues that is testing more than 10,000 people at least daily and sequencing all infections.

It is still unclear how common breakthrough infections occur and how long the virus persists in the body in those cases. Breakthroughs are rare, and unvaccinated people are responsible for transmission of the virus, Dr. Valensky said.

Regardless, the data the CDC is reviewing suggests that even fully immunized people may be reluctant vectors for the virus. “We believe on a personal level that they can be, which is why we updated our recommendation,” said Dr. Valensky said in his email to The Times.

The findings also suggest that vaccinated people who have been exposed to the virus should get tested, even if they feel well. (In the UK, vaccinated people who come into contact with a known case are need to separate for 10 days.)

The new data doesn’t mean vaccines are ineffective. Vaccines still powerfully prevent serious illness and death, just as they were meant to be, and people with breakthrough infections rarely end up in the hospital.

According to CDC data, about 97 percent of people hospitalized with Covid-19 have not been vaccinated, but scientists warned last year that vaccines cannot completely prevent infection or transmission. (may confer immunity from natural infection even less security.)

previous version of virus rarely broke through the vaccination barrier, which prompted the CDC to advise in May that Vaccinated people can go without masks inside the house. But the general rules do not apply to the delta version.

the variant is twice as infectious as the original virus, and a study suggested that the amount of virus in non-vaccinated people infected with Delta may be up to a thousand times higher than in people infected with the original version of the virus. CDC data supports that finding, said an expert familiar with the results.

There have been tales of clusters of successful infections with speed Frequently, groups of people who have been vaccinated have reported sniffles, headache, sore throat, or loss of taste or smell — signs of an upper respiratory tract infection.

But the overwhelming majority do not require intensive medical care, as the immune protection produced by the vaccine destroys the virus before it reaches the lungs.

“We’re still going to see a big, huge, huge impact on the severity of disease and hospitalization,” said Stanford University immunologist Michal Tal. “That’s exactly what the vaccine was made to do.”

Coronavirus vaccines are injected into muscles, and the antibodies produced in response mostly remain in the blood. can make some antibodies their way to the nose, the main port of entry of the virus, but insufficient to block it.

“Vaccines — they’re beautiful, they work, they’re amazing,” said Frances Lund, a viral immunologist at the University of Alabama at Birmingham. “But they’re not going to give you that local immunity.”

When people are exposed to a respiratory pathogen, it can find a foothold in the mucosal lining of the nose—without doing any harm beyond that. “If you went out into the street and swallowed people, you would find people who had viruses in their mucus who were asymptomatic,” said Dr Michael Marks, an epidemiologist at the London School of Hygiene and Tropical Medicine. “Our immune system is fighting these things most of the time.”

But the delta variant appears to thrive in the nose, and its abundance may explain why more people are experiencing breakthrough infections and cold-like symptoms than scientists expected.

Yet, when the virus tries to enter the lungs, immune cells in vaccinated people rapidly spread and clear the infection before it can wreak much havoc. This means that vaccinated people have to be infected and contagious for a much shorter period of time than uninfected people, Dr. Lund said.

“But that doesn’t mean that in those first few days, when they are infected, they can’t transmit it to anyone else,” she said.

To stop the virus from where it enters, some experts have advocated Nasal spray vaccines that prevent the invader from buying into the upper airway. “Vaccine 1.0 should prevent death and hospitalization. Vaccine 2.0 should stop transmission,” Dr. Tal said. “We just need one more iteration.”

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