Why would he need to be weaned by his 15 month check-up? Remicade does NOT pass through breastmilk (according to infantrisk.org, my LC, my GI, and my ped). The only reason to delay live vaccinations was for any leftover Remicade in the system from childbirth, and so my doctors all agreed to hold off live vaccinations until 6 months old.
I have a 4 month old, and am on Remicade infusions. I got influenza a few weeks ago, and she didn't get it at all even though I was still holding her, etc. (I did wear a mask and washed my hands, though). That leads me to think that she isn't getting any of the Remi and isn't immune-system compromised.
Here is that link for infantrisk.org and Remicade:
www.infantrisk.com/content/drug-entry-human-milk