My doctor just tells me to try my best not to be around others with the flu, stomach virus, Pnuemonia and other contagious conditions because when you use immunosepressants like 6MP, Humira, Remicade, Cimizia etc. you are more prone to catch these things & it will also be A LOT harder to fight these things off. Sometimes, anything like a flu can cause a flare up but that isn't always the case.
I still go to school on my Humira(I'm on double the regular dose), and I hang out with friends. I'm actually going to a CCFA walk on saturday & there will be tons of people there. You aren't a cancer patient on extreme doses of Chemo so it isn't like you need to wear a mask or stay in the house all day. Just use common sense & don't share drinks, be around people who are sick & places that host a lot of bacteria(like the gym, nasty locker rooms etc.).
Your doctor told you to avoid people because your nuerophils were down. Your nuerophils were down because of a side effect from the 6mp probably. Not because of the medication its self. Humira is a tottally different drug.
You'll be fine just use common sense. I have MANY friends that are also on Biologics & they play team sports, travel to foreign countries on missionary trips & anything normal people do. I've been using biologics since December & was have been on Humira since Janruary. My only issues have been some Sinus infections that are hard to get rid of(so bad I was having blood drain from my nose in the back of my throat).
I hope it works for you & if your doctor thinks you are THAT susceptible, then follow his advice.