WASHINGTON—President Joe Biden’s administration on Friday announced that the Pentagon had approved the deployment of 1,100 active-duty troops to assist with COVID-19 vaccination efforts in the United States, a number likely to rise in the coming weeks and months. The pandemic has killed more than 447,000 Americans and thrown millions out of work. Andy Slavitt, senior adviser to the White House’s COVID-19 response team, said in a briefing that part of the group would start to arrive in California within the next 10 days. The Pentagon said the 1,110 troops would be broken down into five teams, each with vaccinators, nurses and clinical staff. The deployment is likely just the first tranche of U.S. military personnel assisting in administering vaccinations around the country. White House Chief of Staff Ron Klain last week said the Federal Emergency Management Agency was working with the Pentagon to use 10,000 troops and open 100 …