Vaccines, which teach the immune system to recognize and ward off viruses and other infectious microbes, also take some time to kick in, and aren’t expected to be fully effective until about a week or two after a person receives the final dose. Both the Pfizer and Moderna vaccines require two injections, separated by three or four weeks.
Capitol Hill has long struggled to control the spread of the pandemic within its marble walls, a haphazard effort exacerbated last week as hundreds of maskless Trump supporters stormed the building and forced lawmakers to shelter in confined secure locations across the Capitol complex. Lawmakers, aides and reporters who took shelter in two separate rooms on both sides of the Capitol have been warned about possible exposure to the coronavirus.
Though cases have continued to emerge since the 117th Congress was sworn in nearly two weeks ago, House Democrats have blamed a group of their Republican colleagues who refused to wear masks while waiting in one location for law enforcement to regain control of the building.
Since testing positive in the aftermath of the attack, Representatives Bonnie Watson Coleman, Democrat of New Jersey, Pramila Jayapal, Democrat of Washington, and Brad Schneider, Democrat of Illinois, have all cited the Republican refusal to wear masks during the siege. Representative Ayanna S. Pressley, Democrat of Massachusetts, is in isolation after her husband, who was with her in the room, tested positive, and in a statement said the diagnoses were a consequence of “my callous Republican colleagues” who refused to wear masks.
It was unclear whether Mr. Espaillat took shelter in that room. But on Wednesday, he was among the lawmakers who spoke on the House floor — while wearing a mask — before voting to impeach President Trump for the second time.