The more infectious delta variant has complicated the battle against COVID-19, but vaccines are still doing their job, researchers say. A large study from the UK released Wednesday found that "breakthrough" infections among vaccinated people remain rare, and vaccinated people who do become infected are twice as likely to be asymptomatic, CBS reports. The study published in the Lancet medical journal looked at data on 1.2 million vaccinated adults between early December 2020 and early July this year. It found that less than 0.2% reported a breakthrough infection more than a week after their second shot. Among those who were infected—mostly older people or those with underlying illnesses—the risk of hospitalization was reduced by more than two-thirds.
The British study, which relied on self-reported data, also found that the risk of long-haul COVID—defined as symptoms still occurring more than four weeks after infection—was reduced by almost 50% among vaccinated people who became infected, reports the New York Times. "This is really, I think, the first study showing that long COVID is reduced by double vaccination, and it's reduced significantly," says Dr. Claire Steves, the study's lead author. She says the finding might persuade more young people to get vaccinated.
The delta variant has been the dominant strain in Britain since at least early June, researchers say. "We are at a critical point in the pandemic as we see cases rising worldwide due to the delta variant," Steves says. "Breakthrough infections are expected and don't diminish the fact that these vaccines are doing exactly what they were designed to do—save lives and prevent serious illness." Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, tells NBC that the research shows that vaccines are keeping people out of the hospital and preventing deaths, which is "the goal of these vaccines."
Another study, published in the New England Journal of Medicine Wednesday, found that vaccination dramatically reduced infections among health care workers in California, though breakthrough infections rose sharply after the middle of June. Researchers said this was due to "both the emergence of the delta variant and waning immunity over time, compounded by the end of masking requirements in California and the resulting greater risk of exposure in the community." They found that although many of the workers spent a lot of time around COVID patients, it was still more common for breakthrough infections to happen at home, NBC notes. (Read more coronavirus stories.)