Six-month humoral response to mRNA SARS-CoV-2 vaccination in patients with multiple sclerosis treated with ocrelizumab and fingolimod.

INTRODUCTION: Real-world clinical data suggest an attenuated short-term humoral response to SARS-CoV-2 vaccines in patients with multiple sclerosis (pwMS) receiving high efficacy (HE) disease modifying therapies (DMTs) such as Ocrelizumab (OCR) and Fingolimod (FNG). Long-term humoral response in pwMS treated with these HE-DMTs has been poorly investigated. The aim of our study was to explore: i) the humoral response up to six months after a full cycle of the BNT162b2 mRNA Covid-19 vaccine in pwMS treated with OCR and FNG and to compare it to age- and sex-matched healthy controls (HCs); ii) the relationship between humoral response and clinical and immunological characteristics of the studied population. METHODS: Serum samples were collected from HCs and pwMS treated with OCR or FNG at the following time points: before BNT162b2 mRNA Covid-19 vaccine (T0), and 4 (T1), 8 (T2), 16 (T3) and 24 (T4) weeks after the first dose. Sera were stored at -20 °C and tested for the quantitative detection of IgG antibodies to SARS-CoV-2 trimeric spike protein (Anti-TSP IgG) expressed in binding antibody units (BAU). At T1 neutralizing antibodies (NAbs) titres were assessed. The relationship between Anti-TSP IgG at each time-point and clinical and laboratoristic analyses were analysed by the Spearman correlation coefficient. RESULTS: 47 HCs and 50 pwMS (28 on OCR and 22 on FNG) were included in the study. All HCs mounted a positive humoral response at T1 and preserved it up to six months. At T1 only 57.1% pwMS on OCR (p < 0.001 compared with HCs) and 40.9% on FNG (p < 0.001) had a positive humoral response at T1, with only 39.3% and 27.3% maintaining a positive response at sixth months (T4), respectively. A strong positive correlation was observed between Nabs titres and Anti-TSP IgG at T1 (rho 0.87, p < 0.0001) with NAbs titres significantly higher in HCs compared with pwMS on OCR and FNG (p<0.0001). We also found a strong positive correlation between time-window since last OCR infusion and anti-TSP IgG titres at all time-points (T1 rho=0.58, p = 0.001; T2 rho=0.59, p = 0.001; T3 rho=0.53, p = 0.004; T4 rho=0.47, p = 0.01). In the FNG group we observed a significant correlation between the humoral response measured from T1 to T4 and: i) treatment duration (T1: rho -0.65, p = 0.001; T2: rho -0.8 p< 0.001; T3: rho -0.72, p=<0.001; T4: rho -0.67, p<0.001), ii) disease duration (T1: rho -0.5, p = 0.017; T2: rho -0.6, p = 0.003; T3: rho -0.58, p = 0.005; T4: rho -0.57, p = 0.006), and iii) baseline total lymphocyte count (T1: rho 0.37, p = 0.08; T2: rho 0.45, p = 0.03; T3: rho 0.43, p = 0.04; T4: rho 0.45, p = 0.03). CONCLUSIONS: Our long-term data show a weakened and short-lasting humoral response to SARS-CoV-2 mRNA vaccine in pwMS treated with OCR and FNG when compared with HCs. MS neurologists should take into account the time elapsed since the last infusion for pwMS on OCR, and the lymphocyte count as well as the disease and treatment duration for those on FNG when called to counsel such pwMS regarding the vaccination with the SARS-CoV-2 mRNA vaccine.