And to add to the confusion, there are two strengths of Rebif, so make sure you know which dose was used in whatever research you read. But let me back up a bit…
It’s important to recognise that it’s now known that progression and relapses are different processes, however both cause disability: progression as a gradual increase, relapses as step changes. Trying to differentiate this in a trial is really hard though, especially as it’s perfectly possible to have long drawn out relapses with a sort of cascade of new symptoms, to have mini relapses that don’t last very long, but still add to disability, and to be still getting better more than a year after a relapse. Add in the fact that trials are generally only a couple of years long, and you have a bit of a methodological nightmare And this is the reason that there is a degree of doubt about the claims some DMDs make about their effect on progression: there just isn’t a good way of measuring it in a trial.
An alternative way of looking at it is how long it takes people with RRMS to progress to SPMS if they are / aren’t on a DMD. Unfortunately, different studies find different things so it’s hard to draw any conclusions. If we take the hard line, that it makes no difference, then we have to consider why we bother taking a DMD at all. One argument in favour is that, if we are going to become SPMS anyway, then it’s probably best to have as little disability at that point as possible, because more is coming whether we like it or not. That would be my view anyway.
The fact is that we don’t currently have an effective med for progression. However, it appears that starting on an injectable early on can delay the onset of disability (I think they all report this effect?). The injectables also reduce the number of relapses we have, which means that we avoid the associated disability that they would have brought. They also reduce the severity of the relapses we still have, which means that we don’t get such severe disability from them. It’s none of it a guarantee though - an average relapse reduction of ~30% says that loud and clear: some people do really well on them, some people find they don’t help at all, everyone else is in between. Meanwhile, progression may be happening along side, only marginally reduced.
So, basically what I’m saying is that what works best at delaying or preventing disability depends on what source of disability you mean. If you mean disability from progression, then Rebif is probably more likely to help than Copaxone according to the data, but how much it helps is debatable. If you mean disability from relapses, then I don’t think that there is a whole lot between them if you look over all the data, although Rebif44 did really well in the Campath trial so it may have the edge. But this doesn’t tell you much about Rebif22 which may be all that is on offer in your PCT (I would guess that it’s a coin toss between it and Copaxone). And it may all be irrelevant if, for whatever reason, you cannot risk Rebif’s potential side effects.
Ultimately, therefore, the only right choice is the one that is right for you as an individual.
And that often involves ignoring the data and going with your gut instinct!