What breakthrough infections mean for the Covid vaccines


As coronavirus cases rise once again in the US, experts say breakthrough cases will also rise, but that doesn’t mean vaccines aren’t working.

A series of recent coronavirus infections among vaccinated athletes and government employees has focused attention on a clear increase in so-called breakthrough infections. But while cases involving fully vaccinated people have increased in recent weeks, experts say there is nothing to worry about.

A game on July 15 between the New York Yankees and the Boston Red Sox was postponed due to multiple confirmed cases. A few days later, Kara Ecker, an alternate on the US women’s gymnastics team who had been vaccinated in May, tested positive at an Olympic training camp in Japan. And this week, government officials announced that a White House staffer and a senior communications aide to House Speaker Nancy Pelosi, D-Calif., had tested positive, even though she had been fully vaccinated. Washington DC . The cases came after six members of a delegation of Texas Democrats tested positive for

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According to the Centers for Disease Control and Prevention, more than 161 million people in the US have been fully vaccinated, and breakthrough infections occur in a small fraction of them.

But as the pandemic persists and more communicable forms of the virus spread widely, it is expected that the number of successful infections will increase. Yet studies have shown that most cases in vaccinated people are mild – if a person develops symptoms at all – and research indicates that vaccines still offer strong protection against known forms.

“The reality is that many of these successful infections have been vaccinated by people who test positive, but there’s a difference between testing positive and getting sick,” said Angela Rasmussen, a virologist with the Vaccines and Infectious Diseases Organization at the University of Saskatchewan. he said. Canada.

In other words, people who test positive may have small amounts of the virus in their bodies – enough to be detected by COVID-19 tests but not enough to make them sick.

And because vaccines work by boosting the immune system, it can more quickly identify and attack any invading pathogens.

“If you have a lot of good antibodies, they’re able to attach to the virus before they can potentially cause trouble, and that may or may not reduce your odds of getting sick,” said Dr. Robert, a senior physician and biochemist. Darnell said. Rockefeller University in New York.

Still, there is hope for breakthrough infection because no vaccine is 100 percent effective. In rare cases, fully vaccinated people can become seriously ill and die from COVID-19, but the majority of success cases have been mild or asymptomatic.

This is because vaccines act like screens to block most — but not necessarily all — virus particles from invading the body. Various factors affect the strength of the screen and how small virus particles are able to make it through the barrier, said Dr. Sarah Fortune, an immunologist at Harvard’s T.H. Chan School of Public Health.

A health worker administers the Pfizer COVID-19 vaccination at a mobile immunization clinic on July 16, 2021 in Los Angeles.Irrfan Khan / Los Angeles Times via Getty Images

“These variants are more permeable, so they are better able to get through the screen,” she said. “The other factor is how much virus is trying to enter there, and that is determined by vaccination rates in your local community. It’s how much virus you’re going to be exposed to.”

Vaccines can also reduce the amount of virus in the body, which may limit the ability of people with successful infections to spread it to others, although the effects are not yet well understood. More research is needed to find out what influences transmission, specifically, in asymptomatic success cases.

“It may be that for most vaccinated people who become infected, they don’t make enough virus to infect another person,” said Dr. Janko Nikolich-Zugich said.

Darnell of Rockefeller University said the increase in recent breakthrough infections is not associated with a similar increase in hospitalizations or deaths, which is encouraging evidence that vaccines hold up well despite new and emerging variants. are.

The CDC initially tracked all cases of infection, but by May 1 it had shifted to focusing only on cases involving hospitalization or death. At the time, more than 100 million people in the US were fully vaccinated, and the CDC counted more than 10,000 cases of breakthrough infection.

until 12th July, CDC reports 5,492 success cases In which patients were admitted to the hospital or they died. Three-quarters of the cases involved people over the age of 65. While they are tracked as breakthrough infections, it does not necessarily mean that COVID-19 led to hospitalization or death, especially in patients who were asymptomatic.

Rasmussen said the high rate of hospitalization and death among older adults is not surprising as older people are usually more vulnerable to serious illness from COVID-19. Immunized people or those with underlying conditions are at an equally high risk.

In Israel, where 80 percent of people age 16 and older are fully vaccinated, researchers studied 152 success cases in which patients were hospitalized and found that most people with underlying conditions such as: He was suffering from hypertension, diabetes and congestive heart failure. study, published July 6 Journal Clinical Microbiology and Infection, found that only six cases involved patients with no concomitant disease.

Israel reported this month that the Pfizer-BioNTech vaccine was 93 percent effective in preventing hospitalization and severe disease, but its effectiveness for preventing infection and symptomatic disease fell to 64 percent.

a Separate analysis released June 25 Two shots of the Pfizer-BioEntech and AstraZeneca vaccines were found by Public Health England to be 79 percent effective against symptomatic disease and 96 percent effective against hospitalization with the delta version.

The ability of vaccines to protect against serious disease is critical, Rasmussen said, and is a sign that the shots continue to perform well.

“If we started filling ICUs with people who have been fully vaccinated, that would be a sign that vaccines are no longer effective,” she said.

While vaccines remain highly effective, there is cause for concern if outbreaks continue across the country. The longer the virus is left to circulate, the more likely it is that the pathogen can be mutated in a way that makes it more transmissible, enabling it to cause more severe disease or require vaccines. to help you escape from safety.

“Every pathogen arms race ends badly, because it’s basically evolution,” Fortune said. “What we’re talking about is the virus trying not to go extinct, and evolution is going in favor of transmission. Evolution is going in favor of avoiding vaccines.”

Preventing such an outcome will require a focus on vaccinating as many people as possible in the US and around the world.

“I lose infinitely more sleep over the fact that we have such a large number of unvaccinated people who are at tremendous risk of developing serious disease,” Nikolich-Zugich said. “We shouldn’t be complacent or arrogant about it, but it pales in comparison to the question of how do we get as many people vaccinated.”

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