Infectious diseases are an important consideration in autoimmune conditions such as multiple sclerosis. Infective episodes may trigger relapses and significantly deteriorate the course of the disease. Some immunotherapies may cause increased rates of infection-related adverse events. Thus, infection and vaccine-related issues should be included in the individualized patient-specific treatment strategy and counseling before starting therapy and regularly on treatment. Clinical and epidemiological studies as well as pharmacovigilance data repeatedly demonstrated the safety of the great majority of vaccines in multiple sclerosis patients. Moreover, studies have shown that vaccinations with killed/inactivated vaccines do not increase the short-term risk of relapse or deterioration in multiple sclerosis, whereas infections have been shown to provoke relapses. The available evidence indicates reduced humoral vaccination efficacy on treatment with MS drugs acting on the S1P receptor, natalizumab, and B-cell depleting therapies. Recent data for cladribine tablets suggest the potential of effective immunization in the interval of the two treatment courses and after completion of therapy. Regardless of treatment, vaccine efficacy may be optimized with proper timing of application. Multiple sclerosis patients receiving highly effective therapies should be vaccinated according to general recommendations for healthy adults. Immunization against COVID-19 is highly recommended for all multiple sclerosis patients regardless of age and comorbidities. Preliminary data show the potential of adequate responses in patients treated with cladribine tablets.