Vaccine rates have varied widely between the individual service branches. In July, before Austin’s announcement, the Navy led the way with more 70 percent of its personnel fully vaccinated. At the low end, fewer than 60 percent of Marines met that criteria.

Though Pentagon officials have made clear a mandate is imminent, and that those who refuse risk losing their jobs, inoculation has been voluntary since the vaccines were introduced over the winter — a rare optional task in an organization where orders are the norm. Anecdotally, it appears at least some have viewed the lack of a requirement as grounds to infer the shots might not be safe despite a wealth of evidence to the contrary — or even that they’re unnecessary if their health and physical fitness is otherwise good.

“Just from talking to soldiers, picking their brains, some of the things I’ve heard have been ‘I don’t know the long term effects’ or ‘I just don’t know enough and it worries me,’” said Capt. Javon Starnes, a soldier at Fort Bragg in North Carolina. Starnes detailed his own bout with the virus in an episode of “The 18th Airborne Corps Podcast,” which also featured interviews with other soldiers from the base who espoused a variety of views on vaccinations, ranging from an early desire receive a vaccine to an ongoing reluctance.