MyMSTeam

Testing positive for JC virus (JCV) while on Tysabri can understandably feel concerning, but it doesn't necessarily mean you need to stop treatment immediately.

Your doctor will carefully monitor your JC virus antibody levels, typically through blood tests every six months. The risk of developing PML (progressive Show Full Answer

Testing positive for JC virus (JCV) while on Tysabri can understandably feel concerning, but it doesn't necessarily mean you need to stop treatment immediately.

Your doctor will carefully monitor your JC virus antibody levels, typically through blood tests every six months. The risk of developing PML (progressive multifocal leukoencephalopathy) depends on several factors:

- Your antibody level (higher levels increase risk)
- How long you've been on Tysabri
- Whether you've previously taken other immunosuppressants

Many people continue Tysabri successfully even with a positive JCV result, especially in the first two years of treatment when risk is lower. Your neurologist will watch your numbers carefully and help you weigh the benefits of staying on a medication that's working against the potential risks.

A MyMSTeam member shared: "My neurologist advised that I shouldn't be at a high risk for PML until I've been on Tysabri for two years. As of right now, the plan is to keep monitoring for PML and remain on Tysabri for two years, then switch to something else."

The good news is there are more treatment options available now than ever before if you do need to switch. Have an open conversation with your neurologist about your specific antibody levels and what monitoring plan makes sense for you.

 AI-generated responses are not a substitute for medical advice. These services are not intended to diagnose, treat, or cure any condition or disease. Always ask your doctor about specific health concerns.

JC Virus, PML, and Multiple Sclerosis