Evaluation of the efficacy of the SARS-CoV-2 vaccine additional and booster doses in immunocompromised patients with multiple sclerosis: the COVACiMS study

Studies evaluating COVID-19 primary vaccination with two vaccines reported a blunt response in Multiple Sclerosis (MS) patients under anti-CD20 and sphingosine-1-phosphate (S1P) modulators. An extended primary vaccination (EPV) was recommended in immunosuppressed MS patients. Data on the effectiveness of the EPV and subsequent booster dose are limited. A prospective cohort study (n = 270) was conducted to evaluate the humoral and cellular immunogenicity of the EPV scheme in immunocompromised MS patients (i.e., treated with anti-CD20, S1P modulators, natalizumab, teriflunomide, or dimethyl fumarate) vs. regular primary vaccination in non-treated patients - primary course (PC) cohort. The effect of a subsequent booster dose was also assessed - first booster (FB) cohort . The seroconversion rates were 55% and 56% in anti-CD20 and 75% and 67% in S1P modulators group in PC and FB cohort, respectively, and 100% in the remaining groups. A positive SARS-CoV-2 Spike T-spot was observed in 22% of patients under S1P modulators in PC cohort and 67% in FB cohort; the remaining groups had 75% or more. Similar rates of breakthrough infection were observed in both groups vs. controls. Compared to non-treated MS patients, immunosuppressed patients under anti-CD20 and S1P modulators drugs receiving EPV scheme or booster dose still present lower protection rates to SARS-CoV-2.