Developing an actual vaccine would probably be beyond their capacity, at least initially, but no doubt one or more of the Marines would know about inocculation, which probably reduces the mortality rate by 90%+.
Anywho, it does not appear smallpox was present in the Roman Empire, at least none of the Greek or Roman medical writers describe this highly describable disease.
The most common theory is that Arabs brought smallpox to Europe in the 7th or 8th centuries.
I also believe Marines, at least those posted to 3rd-world toilets, are vaccinated against every damn thing there is.
Not sure. It’s not routine for smallpox immunization, and it is and was present in Egypt. So presumably, marines dropped in that part of the Empire could be affected by it.
Routine inoculation of the US military recuits for smallpox was discontinued in 1990. So 22 years later, it will be only the servicemen over 40 who are still immune to smallpox.
Don’t forget that each MEU is equipped with a field medical unit, too.