My boy was a 2Lt. years ago, and there was no record of him ever being vaccinated. He had to get 7 or so inoculations immediately. He almost passed out in the Infirmary. That kid was in tip top shape too.
The stuff usually surfaces eventually, but if he retained copies of his Orders, the problem should be resolved more easily.
My dad was in the Marine Corps at Cornell University in WW II. He got
all his inoculations there to join the Japan invasion force. I think it was seven like your son got. He walked out of the building and passed out the front staircase.