Effect of cladribine on COVID-19 serology responses following two doses of the BNT162b2 mRNA vaccine in patients with multiple sclerosis

Background multiple sclerosis (MS) patients are treated with immunomodulatory treatments that can influence their ability to develop a protective antibody response to the SARS-CoV-2 vaccine. Vaccine efficacy is important for treatment decision and for patients’ reassurance. The main objective is to assess antibody response to SARS-CoV-2 vaccine in MS patients treated with cladribine. Methods Serology response was tested in 97 participants, 67 MS patients and 30 healthy controls (HCs), using two independent methods, 2–3 weeks following the second dose of the BNT162b2 vaccine. Results HCs (n = 30) and MS patients treated with cladribine (n = 32) had 100% positive serology response against the SARS-CoV-2 spike protein following the second vaccine dose (mean S1/S2-IgG and RBD-IgG:284.5 ± 104.9, 13,041±9411 AU/mL and 226.3 ± 121.4, 10,554±11,405 AU/mL respectively). Comparable findings were observed for untreated MS patients, and interferon beta-1a-treated MS patients (mean S1/S2-IgG: 282.1 ± 100.1, 276.9 ± 94.31 AU/mL respectively). No correlation was found between lymphocyte counts, treatment duration, or time between cladribine dose and vaccination, and serology response or antibody titers. Conclusion and relevance Cladribine treated MS patients are able to produce antibodies to the SARS-CoV-2 mRNA vaccine. In the era of the COVID-19 pandemic, it is reassuring and important for both patients and physicians and will allow to develop consensus guidelines.