COVID-19 breakthrough infections: Can vaccinated people get infected?
People who are fully vaccinated can get COVID, but experts say they’re unlikely to get severely ill.
Staff video, USA TODAY
Everyone wants vaccines to be perfect – and the COVID-19 ones nearly are. Only a tiny fraction of those who are vaccinated end up seriously ill from an infection.
But still, some fully vaccinated people will get sick, some will pass on the virus, and a very small number will die despite their shots.
“The efficacy of the vaccines in preventing hospitalizations and death is unbelievable,” said Carlos del Rio, an epidemiologist and distinguished professor of medicine at Emory University School of Medicine in Atlanta. “It’s not 100%. But nothing in this world is 100%.”
At a time when the infection rate has doubled, many remain unvaccinated and the Delta variant is vastly more contagious than the original, it’s important to recognize vaccines aren’t flawless, he and others said.
“I understand it’s kind of a tough pill to swallow for many people,” said Anthony Santella, a public health expert at the University of New Haven in Connecticut.
Several recent high-profile cases have brought public attention to the fact that people who are vaccinated can still catch the virus.
Last Thursday’s Yankees-Red Sox game was postponed because six Yankees – most, but not all whom were vaccinated – tested positive for the virus. At a homeless shelter in northern California, a number of vaccinated residents tested positive during an ongoing outbreak. And five vaccinated members of the Texas legislature, who had fled the state for political reasons, tested positive for COVID-19 in recent days.
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The common thread for all those infections was that they were caught by routine testing, not because people fell seriously ill, noted Ali Ellebedy, an immunologist at Washington University School of Medicine in St. Louis.
Of the more than 159 million fully vaccinated Americans as of July 12, a reported 5,492 have been hospitalized, and 791 have died related to symptomatic COVID-19, according to the Centers for Disease Control and Prevention.
In May, the CDC stopped tracking all so-called breakthrough infections, focusing only on state and local health department reports of hospitalizations and deaths, so there’s no way to know how many total infections there have been or whether they are increasing because of the Delta variant.
Dr. Leana Wen, an emergency physician and former Baltimore health commissioner, called that decision “inexplicable.”
Without that data, she said, it’s impossible to know how many people are getting infected after vaccination, whether certain people, perhaps senior citizens, are more vulnerable to these breakthrough infections, and how easy it is for people who have been vaccinated and then infected to pass on the infection to others.
“We just don’t know the answers to these questions and that is really preventing clinicians from giving good guidance to our patients,” she said.
Breakthrough cases of COVID-19 are likely growing at the moment because there’s more virus circulating, not because vaccines don’t work against the Delta variant, which now accounts for more than half the infections in the United States, experts say.
Vaccines remain quite effective against catching severe disease from Delta, said Ellebedy, who studies the body’s response to vaccination.
But Delta is vastly more contagious than the original virus, so the unvaccinated are particularly vulnerable.
“If you’re vaccinated, you should not worry about the Delta variant,” del Rio said. “If you’re not vaccinated, you are really in trouble because it’s likely that you will get infected.”
Range of protection
Even healthy people respond differently to vaccination, so it is normal to see variation in protection among the vaccinated, Ellebedy said.
For 95 people out of 100, vaccines from Pfizer-BioNTech and Moderna will provide effective protection.
The problem is, it’s essentially impossible to figure out ahead of time who is most vulnerable. Certain factors like age, obesity and lung disease increase the risk of serious disease if someone is infected. So does the load of virus they inhale and what medications they’re taking, he said.
Some people will test positive despite vaccination, but the immune protection they received will keep virtually everyone from getting seriously ill.
Vaccination also makes people less likely to shed large amounts of virus, Ellebedy said, meaning they are less likely than an unvaccinated infected person to get someone else sick. Anything that decreases the amount of virus replicating itself in the respiratory tract will decrease the probability of passing on that virus, he said. “Transmission will decrease like everything else.”
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