I love Dr Aaron Boster's YouTube videos. Listened to one on infusions yesterday and liked his answer to someone's ? About how to tell if Ocrevus was working.
Paraphrasing, he said: if you had a young woman on birth control, you would know it was working if she did not get pregnant. Likewise, if Ocrevus is working, you won't have progression of disease.
So you look for the absence of new or worsening symptoms.