The B.1.1.7 strain is spreading among adults and kids, and experts say that’s another reason to get vaccinated, fast.

The coronavirus variant known as B.1.1.7, which studies show is both more deadly and more transmissible than the original version of SARS-CoV-2, is now the most common strain circulating in United States, and its growing prevalence has alarmed prominent epidemiologists.

Earlier in the pandemic, not many children were becoming infected with the coronavirus, and they did not appear to be major sources of virus transmission to other age groups. “That changed with B.1.1.7,” says epidemiologist Michael Osterholm, director of the Center for Infectious Disease Research and Policy. “We’re now seeing substantial numbers of outbreaks in schools and in school-related activities.”

In a study conducted in the U.K., where this variant was first detected, more children were infected with B.1.1.7 than other SARS-CoV-2 variants, compared to older age groups. The same scenario is now emerging in the U.S.

A rapidly growing outbreak of COVID-19 in Carver County, Minnesota, has been linked to school-sponsored and club sports activities. In a study done by the Minnesota Department of Health, researchers produced a detailed map of COVID-19 transmission showing that the B.1.1.7 variant caused about a quarter of these cases. A similar outbreak was reported in Wisconsin, where all the children at a Dane County childcare center who tested positive were 6 years or younger.

The upside, if there is one, is that one study suggests younger children were less likely than adults to pass the virus to others. In addition, the current vaccines authorized for use in the U.S. are effective against B.1.1.7 and can help us reverse the course of the pandemic, as long as people also continue to limit exposure by following the current public health precautions and restrictions.

“If you need another reason to get vaccinated, here it is,” says William Schaffner, a physician and professor of infectious diseases at Vanderbilt University Medical Center. “Not only is it more contagious, but when you are infected with it, you’re more likely to get serious disease. And so we’re concerned about it.”