WASHINGTON (AP) — The Biden administration is calling on people to exercise renewed caution about COVID-19, emphasizing the importance of getting booster shots for those who are eligible and wearing masks indoors.

The warning comes as two new highly transmissible variants are spreading rapidly across the country.

The new variants, labeled BA.4 and BA.5, are offshoots of the omicron strain that has been been responsible for nearly all of the virus spread in the U.S. and are even more contagious than their predecessors.

White House doctors pressed the importance of getting booster doses, and says people shouldn’t wait until the fall when vaccines targeted at the variants in addition to the original strain.