The impact of social distancing measures on anti–JC virus serostatus changes before and during the COVID-19 pandemic in US patients with multiple sclerosis

Background: The coronavirus disease 2019 (COVID-19) pandemic offered an epidemiological opportunity to evaluate if isolation and masking affected John Cunningham (JC) virus transmission. Objective: This study aimed to assess the proportion of natalizumab-treated patients who converted to a positive anti-JCV antibody serostatus before and during the pandemic. Methods: Data from TYSABRI Outreach: Unified Commitment to Health (TOUCH) for 22,375 US patients treated with natalizumab with anti-JCV antibody records were assessed in epochs annually from 2017 to 2022. Results: Pre-pandemic anti-JCV antibody serostatus change was observed for 7.4%–7.7%. During the first and second years of the pandemic, 7.3% and 7.2% of patients’ serostatus changed, respectively. Conclusion: The proportion of patients with anti-JCV antibody serostatus change did not significantly differ during the first 2 years of the pandemic compared with prior years. In contrast to seasonal influenza, masking and social distancing had no discernable effect on JCV serostatus change.