DOS contracts are not standard, at least not these days, although I was not operating under some DOS contract, just a MOA with DOS, DoD and the White House.
My son is a contractor in Afghanistan and under the Terms and Conditions of the agreement, health care coverage is provided by the USG. Additionally, I worked such contracts when I was in the Pentagon and the standard terms and conditions were, well, standard. To get out of those coverages required the company to decline.