An aide to House Speaker Nancy Pelosi and a White House official have both tested positive for COVID-19 after meeting with Texas Democrats who fled to D.C. in an effort to block voting legislation, Axios reports. The staffer has not had any contact with Pelosi, according to her spokesperson. Both people were fully vaccinated but the cases come as the Delta variant now makes up 83 percent of all sequenced COVID-19 cases, an increase from 50 percent last week. Brian Monahan, attending physician of the U.S. Congress, later put out a statement confirming that the Delta variant had been detected in the Capitol and urging members of Congress to wear a face mask in crowded indoor spaces. COVID vaccines are extremely effective in preventing infection and, if a breakthrough infection occurs, it’s more likely to be mild.

The U.S. initially outpaced the world in vaccinating its citizens but has struggled with slowing demand. About 56 percent of Americans have received one dose of the vaccine, short of President Biden’s weeks-old goal of 70 percent by July 4.