How common is it to flare between biologics?

Just switched from Enbrel to Simponi and while Enbrel wasn’t doing the trick, it seemed it still did more than I thought because I’m flaring hard now.

I just took one dose of Simponi though so I’m not at a point where efficacy is really expected. But I’m kinda shocked how bad I feel. The transition is NOT smooth lol.

My doctor says stopping one biologic and starting another is kind of like being untreated while the new one hasn’t fully kicked in yet. He says flares can be common in the transition period.

Is this true? Flares between biologics are nothing to worry about?

Thanks!