This is what Professor G has to say about people with an inability to create antibodies to Covid due to their being on an anti-CD20 disease modifying therapy. (This includes Ocrelizumab/Ocrevus.) There is a suggestion that people on Ocrevus and other anti-CD20 DMDs have the vaccine at least 3 months after the last infusion and 4 weeks before the next. Or some msologists (ie MS specialist neuros) are missing the next dose of Ocrevus until the B cells have reconstituted.
If you are on Ocrevus, do talk to your neurologist about the possibility or necessity of delaying your next infusion.
Also, he mentions Fingolimod, apparently it seems to blunt vaccine effectiveness. But in this case, he is recommending that people continue with the drug and have the vaccine and boosters. People on Fingolimod who catch Covid don’t seem at greater risk of severe Covid than the wider population. The exception to this is people with co-morbidities, ie people who are in other risk groups (eg, diabetics, the obese and with high blood pressure).
If you are on a drug that concerns you, talk to your neurologist about it in the light of Prof G’s information.