Incidence of seroconversion and sero-reversion in patients with multiple sclerosis (MS) who had been treated with natalizumab: A systematic review and meta-analysis

•Seroconversion is important in patients with multiple sclerosis.•The incidence of seroconversion was reported between 6% and 41%.•The incidence of seroreversion was reported between 1% and 11%.•Incidence of seroconversion is higher in European/American countries.