Introduction
multiple sclerosis, RRMS
DISEASE, MULTIPLE SCLEROSIS
Since its approval for the treatment of relapsing–remitting multiple sclerosis (RRMS), natalizumab (NTZ) has shown significant benefits in reducing disease activity [Since 2019, ocrelizumab (OCR) has been approved as a highly effective treatment for RRMS [In both social and health research, a study design based on a natural experiment has been proposed [This study aimed to compare therapeutic strategies for switching to OCR or continuing on NTZ after at least two years of NTZ treatment based on JCV serology, which works as a natural pseudo-randomization factor. We compared the disease activity between the two groups during follow-up.