Austin released a message to the troops saying that after consultations with senior civilian and military officials, making vaccinations mandatory is the best way forward.

More than 73 percent of active-duty personnel have received at least one shot of the vaccines to date, according to the Department of Defense.

“I strongly support Secretary Austin's message to the force today on the Department of Defense's plan to add the COVID-19 vaccine to the list of required vaccinations for our service members not later than mid-September,” Biden said in a message released by the White House. “Secretary Austin and I share an unshakable commitment to making sure our troops have every tool they need to do their jobs as safely as possible. These vaccines will save lives. Period. They are safe. They are effective. Over 350 million shots have been given in the United States alone. Being vaccinated will enable our service members to stay healthy, to better protect their families, and to ensure that our force is ready to operate anywhere in the world.”

The Food and Drug Administration is expected to give full approval to the vaccines, possibly by the end of the month, Kirby said. If that happens, Austin will immediately add the vaccines to the mandatory military list, Kirby said.

The services have time to plan how they will implement the program, and they have been working on how they will vaccinate the rest of the active and reserve component. Kirby said there is no shortage of vaccines and the department does not think this will be a limiting factor.

A full third of Austin's message to the force urged service members not to wait: To get the vaccine right away. “You can consider this memo, not just a warning order to the services, but to the troops themselves,” Kirby said. “We certainly hope that they will take advantage of the opportunity to get the vaccines now that are available now to them on a voluntary basis. That's obviously the potential effect that we'd like to see achieved as a result of the secretary's message. But if they don't, eventually we're going to get to a mandatory sort of regimen and we'll take care of it then.”