Reply #1: It was probably the anthrax vaccine actually

[TZ]

That vaccine is notorious for having bad sides. The US government has asked the one current manufacturer of the vaccine to make a new one that requires less than the 6 boosters currently given, which indicates to me that they are unhappy with the current product more so than its too many boosters. There is also a post exposure vaccine like (its not a true vaccine) product for anthrax that just did get fasttracked by the FDA. It can't be a flu vaccine, because they are only given at certain times of the year. And I am very aware of what vaccines are being developed right now and I can pretty much tell you that given the shortage of people the military has they are not gonna be testing what's being developed right now. Anthrax has caused this problem in the recent past and was re worked. Of course you can argue its best not to give milatary any vaccines so they can be free to pick up the various nasty infectious diseases and bring them back to the US as well. (see a story about the military personnel spreading Leishmaniasis)
This Anthrax vaccine has actually caused quite a few problems in the military since about the first Gulf War.