COVID-19 vaccines are highly effective in protecting against serious illness, but they do not protect against "long COVID" in people who become infected despite vaccination, new data show.
For six months, researchers tracked 9,479 vaccinated individuals diagnosed with COVID-19 and about the same number of infected patients who had not been vaccinated.
Compared to the unvaccinated patients, people with so-called breakthrough infections were "at a much lower risk of severe complications of COVID-19" such as the need to be admitted to an intensive care unit, requiring breathing assistance, or developing a blood clot in their legs or lungs, said Maxime Taquet of the University of Oxford.
But other complications of the virus, including the syndrome of lingering symptoms known as long COVID, occurred at similar rates regardless of vaccination status, his team said in a paper posted on medRxiv ahead of peer review.
In people over age 60 with breakthrough infections, vaccines protected against COVID-19 complications only weakly or not at all, Taquet noted.
"Vaccines are still an excellent way to prevent any complication of COVID-19 (including long COVID) since they prevent infection in the first place," Taquet said. "However, these findings show that those who get infected despite being vaccinated should remain vigilant about potential complications of their illness."