Type D Visa Health Care Question (Gent)

I'm trying to obtain a trailing spouse visa from the US to Belgium for August but I have a question regarding proving health insurance -- Its unclear whether my husband's job will cover me. I have a job lined up predicated on obtaining the visa that will provide social security benefits. Would a letter from my future employer about social security suffice for visa purposes or do most expats take out expat insurance for this purpose/in addition to Belgian insurance. Any thoughts would be helpful.