I'm on Remicade, a sister medication to Humira, and I have not experienced any side effects from it despite being on it for 3.5 years now.
Some report general fatigue after they've taken their medication but usually nothing all that serious or concerning. These medications do slightly weaken your immune system's abilities to fight off infections, specifically those infections that typically require antibiotics to treat (UTI's, bronchitis, sinus infections, etc.), so if you are prone to getting those, then seek treatment earlier as it will hit harder and faster than your normal. You might be sick an extra time a year, and it might last a little longer and be a little more severe than your normal (a cold that would normally last a week might last several extra days and you might have an extra day of worse symptoms).
I haven't been sick any more than my normal, I'm just extra vigilant with hand washing during cold and flu season, as they're mostly transmitted via handshakes, door handles, person-to-person.
Moderator Ulcerative Colitis
John, 39, UC Proctosigmoiditis
Rx: Remicade @5mgs/kg/6wks; daily 75mgs 6MP, 4.8g Lialda, and 2X rowasa
Invisible Illness: If I looked as bad as I feel then I'd scare your children!