Poor immune response could be an indication of something more. Taking sups to boost up can't hurt but it should be worth your while to try and find out why your immune system is not fighting infections. There can be an underlying cause that can be easily treated. Gingivitus is a good example. I'm not saying that's the problem, just using it as an example. Everyone has it to some degree but the bacteria produces toxins that inflame the gums below the gum-line so you may not even know it. You could have a low grade fever, get sick often, and feel tired all the time and all you need to do is go see your dental hygienist. So if I were you guys, I would go get the works. Have them check your mouth, teeth, bloodwork, upper/lower GI, mental state, etc. Nobody should have to live with getting sick every month.
I've had SARS, ebola, and the avian flu all at once and it only lasted the weekend. It probably wouldn't have lasted that long if I didn't eat that Schwann's ice cream. I should have known that Uncooked Pork Swirl would be trouble.