Hope you plan your expedition wisely. "Be prepared".
Regarding your question about vitamins, no I don't take vitamins except what is in the fruits, veggies and other foods I eat. I don't believe in taking pills when there are other alternatives. I don't even take tylenol or other pain medicine for headaches. Nothing a good rest can't handle. I have never had a flu shot. My doctor asks me every year. I tell him that if I was meant to receive a shot of the flu virus, (which is exactly what a flu shot is), that I am sure it will find me all by itself!
I believe our natural immune system was given for a purpose. It cannot serve us properly if we continue to break it down with synthetic toxins. There is a reason children get the mumps, measles and chicken pox, or at least they did when I was growing up. Once you get them, you cannot get them again. Your body is now "immune" to it. This strengthens the immune system and prepares it for adulthood. No continued treatments of vaccines or innoculations.
I also believe that the common cold and flu viruses are God's gift to mankind. When your immune system is allowed to fight these viruses without the aid of synthetics, it strengthens the immune system. In the long run you become totally immune to those viruses. What I have now is not a full fledge flu. It is what I call a "touch up".