Vaccination Breakthrough Cases Resolving Into Long-Covid And Deadlier Variants

npr  |  There's more potentially worrisome news for vaccinated people: In very rare cases, people experiencing breakthrough infections may be at risk for long-COVID symptoms.

That's according to a small new study of fully vaccinated health care workers in Israel, published Wednesday in The New England Journal of Medicine.

Data from Israel pic.twitter.com/Qmu4ZDtN7a

— Irene Tosetti (@itosettiMD_MBA) July 10, 2021

The study confirmed what's already known: That it's very rare for fully vaccinated people to get infected or sick with COVID-19. But it also found lingering COVID symptoms did develop in a handful of breakthrough cases.

Researchers studied 1,497 vaccinated health care workers at the Sheba Medical Center in Israel. Among them, only 39 got infected despite their inoculations. Of those, seven — or about 19% — developed symptoms that lasted at least six weeks, including headaches, muscle pain, loss of taste and smell and fatigue.

"It's really disturbing," says Dr. Gili Regev-Yochay, director of the infection, prevention and control unit with the Sheba Medical Center and an author of the study.

"If this is what we're going to see with all of the even mildly symptomatic infections that we're seeing now, it's definitely worrisome," she says.

New data suggests that fully vaccinated individuals are not just contracting COVID, but could be carrying higher levels of virus than previously understood, facilitating spread, my NBC News colleagues are reporting. New indoor masking guidance expected today.

— Ken Dilanian (@KenDilanianNBC) July 27, 2021

Regev-Yochay and others stress that the results need to be confirmed by additional research involving many more patients who are followed for much longer. It could be a false alarm, the symptoms could be much rarer, or they could resolve far more quickly than the months of symptoms that typically plague those suffering from long COVID.

Experts stress that vaccination remains highly effective at preventing the most severe consequences of infection: hospitalization and death.

Nevertheless, other researchers agree the findings are cause for additional investigation.

"We had hoped that when you get vaccinated and even if you did have a breakthrough infection you would have enough of an immune response that would block this protracted symptom complex now known as long COVID," says Dr. Eric Topol, a professor of molecular medicine at Scripps Research.