House Democrats quash a G.O.P. effort to end the chamber’s mask mandate.

House Democrats defeated a Republican-led effort on Wednesday to urge the attending physician to update the chamber’s mask mandate, panning the attempt and seizing the opportunity to point out the minority party’s paltry vaccination rates.

Republicans, led by Representative Kevin McCarthy of California, the minority leader, and a slate of doctors who now serve as lawmakers, tried to turn the tables on Democrats and paint them as being opposed to science after leadership decided to abide by an existing rule requiring lawmakers to wear masks on the House floor.

They introduced a bill directing the attending physician to “take timely action to provide updated mask-wearing guidance” consistent with new recommendations from the Centers for Disease Control and Prevention stating that fully vaccinated individuals no longer need to wear masks indoors.

“The continued House mask mandate sends the erroneous message that the efficacy of the vaccines cannot be trusted,” Mr. McCarthy’s resolution read, adding, “Those who have not yet received the vaccine pose no real threat to those who have been vaccinated.”

But the resolution, which was defeated in a party-line vote, 218 to 210, did not mention that several Republican lawmakers have publicly refused to take the Covid vaccine, and that dozens more have refused to disclose whether they have been vaccinated.

Mr. McCarthy said in March that 70 percent of House lawmakers had been vaccinated. That number has most likely increased in the months since, and House Democrats have since reported a 100 percent vaccination rate. But a CNN survey this month found that only 45 percent of House Republicans were willing to say they had been vaccinated.

In guidelines issued by his office on Wednesday, the attending physician, Dr. Brian P. Monahan, argued that the uncertainty around how many members of Congress had been vaccinated — as well as the sheer number of lawmakers gathering in one location — justified continuing the mask mandate.

“Extra precautions are necessary given the substantial number of partially vaccinated, unvaccinated and vaccine-indeterminate individuals,” Dr. Monahan wrote. “Additional medical safeguards are required to reduce the risk of coronavirus outbreak in this vital group.”

In recent days, several hard-right House Republicans, some of whom have indicated that they will not get vaccinated, have refused to wear masks on the House floor as mandated by the attending physician, incurring fines of up to $500.

“If Minority Leader McCarthy wants to be maskless on the floor of the House of Representatives, he should get to work vaccinating his members,” Drew Hammill, a spokesman for Speaker Nancy Pelosi, said in a statement, saying the resolution had “zero basis in science or reality.”