Pretty much immediately after I wrote my last post, it dawned on me that America's over reliance on vaccines is actually a massive problem from a defensive standpoint. You don't need a huge budget in order to weaponize novel agents; just send an infected Filipino on a vacation to Disneyland. I suppose if the enemy were trying to cause mayhem among the troops, they'd likely want to factor in the vaccination schedule. If I remember correctly, the titers drop off significantly by the second year.
Then a secondary line of attack, especially on highly vaccinated populations would be timed with vaccinations. In this case they wouldn't be the standard diseases people are vaccinated against, but diseases able to take advantage of the reduced immunological state that occurs immediately upon being vaccinated.
Not only would this be relatively cheap, it would be moslty safe for people from foreign countries that have already been exposed to these diseases to handle the live cultures in various ways and figure out how best to infiltrate various American institutions- including military bases.
For the military, this is unlikely to result in much death, but the reduction in capability and morale from having a base full of sick people is likely on a par with the reductions found among those with high injury rates, like those having to deal with land mines.
The effects in the American population could be much more devastating, largely because infants have always had need to depend on their mother's immune system, and many of those immune systems aren't up to the task, nor are the mothers necessarily breast feeding anyway.
Given the continued scapegoating of the non-vaccinated- someone is actually coming out with a book about how American freedom allows infectious disease to spread, an enemy would have a strong lead time, possibly able to start multiple epidemics before officials would even begin to understand they were under attack.
Secondarily, the likely fascist policy response our government would make to multiple outbreaks of diseases previously thought to be managed or eradicated would key right into terrorist strategy- essentially the response of the government to the 'terror' delegitimizes the ostensible democracy. Another potential weapon for a Fourth Generation War.