An orphan medicinal product, eculizumab is approved in Japan and globally for treating paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Eculizumab therapy can cause late complement pathway deficiencies that predispose patients to meningococcal infections. Although meningococcal vaccinations are typically considered mandatory for eculizumab therapy, no approved vaccine is available in Japan as of March, 2014. Advertising unapproved, privately imported pharmaceuticals is prohibited under Japanese pharmaceutical law; detailed information concerning the unapproved meningococcal vaccines is therefore not widely available. The situation jeopardizes the safety of patients receiving eculizumab therapy, and Japanese clinicians are advised caution when prescribing this therapy.