A new yearlong study from the United Kingdom found that people vaccinated against COVID-19 can be just as likely to spread the delta variant as those who were unvaccinated.

The study, published Thursday in The Lancet, found that the vaccinated and unvaccinated, when infected with the Delta variant, carry similar viral loads at the peak of their infections. Viral load, or how much of the virus a person is carrying at a particular time, can be viewed as an indicator of contagiousness, most experts say.

Vaccinated people are just as likely as unvaccinated people to spread the delta variant to contacts in their household, a yearlong study found https://t.co/2Px9LM5WcB

— Bloomberg (@business) October 28, 2021

Researchers were examining the prevalence of household transmission among vaccinated and unvaccinated individuals infected with the delta variant. They found that while peak viral loads were similar, the vaccinated saw their viral loads decrease faster, making them less contagious over the course of their infection than the unvaccinated.

The study also found that vaccinated members of the same household were about one-third less likely to get infected by another vaccinated person than the unvaccinated. (RELATED: Some Of The CDC’s Own Advisers Doubt The Need For Universal COVID Boosters)

Only 621 participants were tracked in the study, 71 of whom were infected with the delta variant. “Although vaccines remain highly effective at preventing severe disease and deaths from COVID-19, our findings suggest that vaccination is not sufficient to prevent transmission of the delta variant in household settings with prolonged exposures,” the researchers concluded.

The findings are consistent with prior research indicating that while vaccines reduce transmission by some amount, the vaccinated can carry similar viral loads to the unvaccinated at particular points in time.