Vaccinated People May Spread the Virus, Though Rarely, C.D.C. Reports
In another unexpected and unwanted turn of the country’s pandemic, fully immune people with so-called breakthrough Delta variant infections can pass the virus to others as easily as unvaccinated people, the Centers for Disease Control and Disease Control said. Prevention in a report released on Friday.
Vaccines remain powerfully effective against serious illness and death, and infections in those vaccinated are considered relatively rare. But the revelation follows a slew of other discoveries this week about the Delta variant, all of which have rocked scientists’ understanding of the coronavirus.
An internal agency document, which was obtained by The New York Times Thursday evening, raised even more poignant questions than the report released on Friday, which mainly focused on a huge cluster of infections in Provincetown, Massachusetts. .
Taken together, the data collected by the CDC calls into question the country’s plans to return to offices and schools this fall, and reignites tough questions about the masking, testing and other precautions Americans hoped were behind them. .
Very immediately, research informed the agency’s decision this week to advise even vaccinated Americans to resume wearing masks in indoor public spaces in communities where the virus is on the rise.
Even the vaccinated carry high levels of the virus if they are infected, the agency concluded, making it likely that they can transmit the virus as often as the unvaccinated. If so, they may contribute to the increase in new infections – although probably to a much lesser degree than unvaccinated ones.
“We spent so much time, energy and treasure trying to figure out this damn virus last year, and how it works and everything it does,” said Dr Robert Wachter, chairman of the department of medicine from the University of California, San Francisco.
Learning how different the Delta variant is from the original virus is “just shocking,” he added. “The brain doesn’t like to keep shaking like this.”
Outbreak studies have shown Delta to be much more contagious than the original virus or seasonal flu and as contagious as chickenpox, according to the internal document released within the CDC
Major infections among those vaccinated were always expected, but until the arrival of the Delta variant, vaccinated Americans were not to be sources of new infections.
Vaccines remain the only reliable shield against the virus, whatever its form. Nationwide, around 97% of people hospitalized with Covid-19 are unvaccinated, CDC data shows
“Full vaccination is very protective, including against Delta,” said Angela Rasmussen, researcher at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada.
“Masks are a wise precaution, but most of the transmission is among the unvaccinated and that is always the most at risk,” she added.
The research gathered underscores the urgency of accelerating the pace of vaccination in the United States and reducing the number of people at risk of serious illness. This week, the vaccination rate in the European Union exceeded that of the United States for the first time.
The agency stepped up concerns about the spread of the virus in its report on Friday, even urging jurisdictions with undetectable levels of the virus to take precautions. But the CDC’s internal document sounded a much more alarming note, arguing for universal masking – for everyone, regardless of local levels of transmission – and recommending that the agency “recognize that the war has changed.”
With the daily case count reaching nearly 72,000 cases on average as of Friday, people vaccinated with young children, aging parents, or friends and family members with weakened immune systems may need to wear face masks. protect vulnerable people in their orbit – even in communities with lower infection rates.
Indeed, the questions facing Americans today seem almost inexhaustible, almost insoluble. Should companies really send their employees back to their workplaces if vaccinated people could occasionally spread the variant? What does this mean for stores, restaurants, schools? Are unmasked family reunions off the table again?
Delta’s unpredictable nature humbled scientists who predicted that the virus would cause mostly sporadic outbreaks in areas with low vaccination rates. In Britain, where the variant appears to subside after an outbreak, vaccinations have been rolled out by age and a much higher proportion of people over 50 are vaccinated than in the United States.
But vaccination rates are much more uneven in the United States, said Bill Hanage, an epidemiologist at Harvard TH Chan School of Public Health. “The upshot is that what Delta is doing in the UK is not necessarily what it is going to do in places where vaccination is more varied,” he said.
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“Things are going to be worse than they would have been” without the variant, he added. “But they’re going to be a lot better than they could have been without the vaccination.”
In the report released Friday, the agency described a single outbreak in Provincetown, Massachusetts, which quickly spread to nearly 469 cases in the state on Thursday, three-quarters of which were fully immune.
The city’s experience this month strongly supports the idea that even fully immune people can unintentionally spread the virus. “We think that on an individual level they could do that, which is why we’ve updated our recommendation,” CDC director Dr. Rochelle Walensky said in an email to The Times this week.
The outbreak began after more than 60,000 revelers celebrated July 4 in Provincetown, gathering in densely populated bars, restaurants, guesthouses and rental homes, often indoors.
By July 10, there had been a noticeable increase in cases among county residents, including those who were fully immune. A week later, the county’s daily average fell from zero cases to 177 cases per 100,000 population.
“Vaccines are like waders,” said Dr Rasmussen. “They keep you dry if you cross a river, but if you are too deep and water will start to flow over it. This appears to be what happened during the Massachusetts outbreak. “
Three-quarters of those infected in Provincetown reported having a cough, headache, sore throat or fever – symptoms of an upper respiratory infection – and 74% were fully immune.
Of the five people hospitalized, four were fully vaccinated – one with the Pfizer-BioNTech vaccine and three with the Johnson & Johnson vaccine. Two of the patients had underlying medical problems. Genetic analysis of 133 cases identified the Delta variant in 119 cases and a closely related virus in one case.
Scientists even warned last year that vaccines might not completely prevent infection or transmission. But experts did not expect these events to figure significantly in the fight against the virus, nor the speed at which the Delta variant would cross the country.
“I thought two months ago that we were on the bump,” Dr Wachter said. In San Francisco, the most vaccinated large city in the country, 77% of people over 12 are vaccinated.
And yet, the hospital where he works has seen a sharp rise, from a case of Covid-19 on June 1 to 40 now. Fifteen of the patients are in intensive care.
“If getting 70 or 75 percent immunity doesn’t protect the community, I think it’s very difficult to extrapolate what happens to a place that is 30 percent vaccinated,” said Dr Wachter. “Humility is perhaps the most important thing here.”
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