To thoroughly evaluate safety of 7-valent pneumococcal conjugate vaccine (PCV7) in children with INS in remission, we will investigate a possible association of vaccination with increased risk for recurrences of INS. We will also study immunogenicity and kinetics of immune response in INS patients and healthy subjects and the effect of different types of treatment on primary immune response and antibody persistence at 12-14 months following vaccination with PCV7.