President Joe Biden rolled up his shirt sleeve and received a COVID-19 vaccine booster inoculation on Monday, hoping to provide a powerful example for Americans on the need to get the extra shot even as millions go without their first.

"Boosters are important, but the most important thing we need to do is get more people vaccinated," he said, noting that about 23% of people in the United States have not received a shot.

In getting the booster, Biden dismissed criticism that the United States should distribute more vaccines worldwide before allowing boosters at home.

While scientists are divided over the need for booster shots when so many people in the United States and other countries remain unvaccinated, Biden announced the push in August as part of an effort to shore up protection against the highly transmissible Delta variant.