Immunogenicity of a seasonal influenza and a pneumococcal polysaccharide vaccine in multiple sclerosis patients under disease modifying therapies: A single-center prospective study

•Influenza and pneumococcal vaccine immunogenicity in multiple sclerosis was studied.•Significant immunogenicity was noted for influenza but not for the PPSV23 vaccine.•Rituximab had an effect on the height of the response.•No safety concerns were raised. Immunogenicity of influenza and pneumococcal vaccines varies and requires further elucidation in patients with multiple sclerosis (MS) under treatment with disease-modifying therapies (DMTs). Adult MS patients who consented with vaccination after standard-of-care consultation by their treating physicians were enrolled. All received a single dose of an inactivated quadrivalent influenza vaccine and of the 23-valent pneumococcal vaccine. A blood sample was collected before and after four weeks of vaccination for measurement of antibodies against Influenza A, B and S. pneumoniae. Patients were followed-up for adverse events and MS relapse for 12 months. One hundred and seventy-two patients (65.7 % female, mean age 42 ± 13 years old, mean MS duration 7.6 ± 7.2 years, 81.4 % under DMTs) were enrolled from November 2019 to March 2020. Antibody measurements were available for 151 patients. Seropositivity for anti-PPSV23 did not differ between baseline and at 4 weeks of follow-up (n = 56, 37.1 %). There was a significant increase of absolute antibody titers post-vaccination for both influenza A and B (p