I'll tag some parents whose kids have had reactions: my little penguin, Clash.
Is Remicade actually working for him considering his levels are zero? Reactions can worsen over time, so that is probably why your doctor wants to switch.
I will say that we gave up on Remicade when it stopped working. My daughters did not have reactions, it just stopped being effective. They did not have antibodies.
Both my girls have been Humira and that worked for them too. One is still on on it, several years later.
Humira is a shot and it does hurt quite a bit. My girls did not like it but got used to it and understood that they needed it. We used ice and did the shot while watching TV, so they were distracted. Other parents have added Lidocaine to the shot to help with the burning.
Humira is going to come out with a new formulation soon, to make the injection less painful. It has already been released in Europe. So keep in mind the painful shot is only temporary.
All that said, Humira worked better than Remicade for my girls. Has your doctor considered adding something like MTX/6MP to Humira to prevent the formation of antibodies? Many GIs are doing that now so your kiddo can stay on the drug.
If you are uncomfortable with switching, I would get a second opinion. But considering your son is reacting, it really is the next step.
There are only a few options for kids, but they are increasing.
Right now Remicade and Humira are approved. Cimzia, Entyvio, Stelara and Simponi are used off-label.