On Monday, just hours after the Pfizer vaccine was granted FDA approval, the Pentagon announced that it was set to require vaccinations for all service members. Except, around one-third of US service members have refused the jab. In July, between 60% and 70% of personnel were fully vaccinated – with the Navy being the most vaccinated and the Marines being the least, according to the Washington Post.

So fast forward to today when in an apparent gamble that could see a third of the US military resign en masse, defense secretary Lloyd Austin ordered service members to “immediately begin” receiving the COVID-19 vaccine, according to a Pentagon memo released Wednesday.

“To defend this Nation, we need a healthy and ready force. 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,” Austin wrote in the memo seen by Reuters.

No timeline was given for when troops are required to get the shot, but Austin said he directed service branch secretaries “to impose ambitious timelines for implementation,” and to report to him regularly on their progress.

Roughly 800,000 active duty, National Guard and Ready Reserve troops have yet to receive the COVID-19 vaccine, according to the latest numbers from the Defense Department. But with the Food and Drug Administration giving full approval to the Pfizer vaccine earlier this this week, Austin was able to add it to the list of 17 required shots service members must get when they enter the military or before they deploy overseas.

As we noted two weeks ago, according to a 2018 DoD military demographics report (p. 40), the average active-duty military member is 28.2-years old, which according to The Economist‘s estimated Covid-19 risk calculator, puts the risk of death for active-duty men at less than 0.1%, and hospitalization at 2.6%. For active-duty women, the risk of death is also less than 0.1%, and hospitalization 1.6%.

In addition to the extremely low mortality rate – combined with the fact that vaccinated individuals can still contract and transmit Covid-19, albeit at lower rates, perhaps the largely young and fit members of the military aren’t about to change their mind – except now they may lose their jobs.