The United States Department of Defense has ordered the military service members to get fully vaccinated against COVID-19 following the approval of Pfizer's coronavirus vaccine earlier this week by the Food and Drug Administration. The order came through a memo released by Secretary of Defense Lloyd Austin on Wednesday.

The memo directed all personnel of the United States military, including reserve forces and National Guard, to "immediately begin full vaccination". according to US media reports.

The memo read, "After careful consultation with medical experts and military leadership, and with the support of the President, I have determined that mandatory vaccination against coronavirus disease 2019 (COVID-19) is necessary to protect the Force and defend the American people", according to reports from CNN.

Earlier this month, the Pentagon announced that it was waiting for the Food and Drug Administration to clinically back any of the COVID-19 vaccines available in the country before giving the orders.

A day before the memo was released, it was sent to senior authorities of the Department of Defense. This included commanders of the Defense Department Field Activity Directors and Combatant Commands and Defense Agency.

About 76% of the United States active-duty military personnel have already received one shot of the COVID-19 vaccines while 68% of the forces have been fully vaccinated, according to media reports citing Pentagon spokesperson John Kirby.

Kirby said in a press briefing that Secretary Austin "has made clear his expectation to the military departments that he wants them to move with some alacrity here and get the force fully vaccinated as fast as possible", CNN reported.

The new vaccine mandate for the armed forces will be exempting personnel under certain circumstances. These include preexisting and underlying medical conditions, participation in clinical trials of vaccines, religious reasons and advisement from doctors.

So far the Pentagon has only mandated the Pfizer vaccine and may take further measures if and when the Food and Drug Administration approves other variants.