Senate Minority Leader Mitch McConnell on Tuesday urged more Americans to get the coronavirus vaccine, as hesitancy toward the shots remains persistent among Republicans and some of his colleagues continue to cast doubt on the vaccinations.

"I'm a huge fan of vaccinations as a polio victim myself when I was young," McConnell told reporters at a Capitol news conference Tuesday. 

McConnell underwent extensive polio treatment as a boy in order to walk and marveled at the science that produced "three highly effective vaccines" against coronavirus when it took decades to find a vaccine for the crippling disease of polio. 

"I'm perplexed by the difficulty we have in finishing the job," McConnell said of stamping out the COVID-19 virus once and for all.

"We're in the red zone, but we're not in the end zone yet," he said.

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Republicans remain more skeptical about getting the shots. Fox News polling in June found that 55% of Republicans surveyed said they got the coronavirus vaccine, compared to 78% of Democrats and 59% of independents. 

"We need to finish the job and part of it is just convincing the American people of the importance of doing this," McConnell said.

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The pace for vaccinations has slowed in the United States just as the much more contagious delta COVID-19 variant is becoming the dominant strain of the virus. Coronavirus cases are increasing in many states around the country, with Louisiana seeing a significant upward trend, according to a seven-day average from Johns Hopkins University. 

Sen. Roy Blunt, R-Mo., said the fight right now is "vaccine versus variant." Joining McConnell at a news conference Tuesday, Blunt said the best way to stop the development of the more dangerous variants is to have more people vaccinated. 

"We are not nearly in as bad of a place as we were, but we're not nearly in as good a place as we would all like to be," Blunt said.

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The Biden administration came up just short of its July Fourth goal of having at least 70% of adult Americans at least partially vaccinated against COVID-19. According to the Centers for Disease Control and Prevention, 67.7% of adults in the country had received at least one vaccination shot as of Tuesday. 

Some GOP House members and others have spoken out against the Biden administration's latest push for vaccinations that includes door-to-door outreach by volunteers in parts of the country with low vaccination rates. 

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And some GOP lawmakers have fueled doubts about the shots themselves, including Sen. Ron Johnson, R-Wis., who recently held an event with people who said they suffered adverse health effects from the vaccinations. 

Asked about Johnson's efforts, McConnell declined to criticize his colleague, saying: "I can only speak for myself."