Immune system boosters?

I've recently contracted a virus and need some good things to boost my immunity, especially because I will be starting my period and that lowers your immune system. I exercise and drink lots of water and plain tea and get lots of vitamin c but what are some other good things that boost immunity? I'm also a vegetarian but am pretty fine with my iron supply, I don't take iron supplements and don't want to. I try to keep it as natural as possible. Thanks a bunch!