Our objective was to demonstrate that nephrotic children at disease onset and under high-dose prednisone respond to vaccination with 23-valent pneumococcal vaccine (PV). We compared the serological response after PV in 30 children with nephrotic syndrome, directly after initiation of prednisone therapy (60 mg/m2 body surface area) at disease onset (group 1), with the response in 13 patients who received the vaccine while in remission (group 2). Safety was studied, comparing disease course in group 1 with those in patients who did not receive any PV (group 3). In group 1, 23-valent PV antibody (Ab) levels increased tenfold after 1 month and remained increased after 1 year (P < 0.01). Ab response in the short term and in the long term was not different from that of patients in group 2. Serum albumin, age, or immunosuppressive drugs did not influence Ab response. Disease courses in groups 1 and 3 were not different. In conclusion, nephrotic children on high-dose glucocorticoid therapy respond to a 23-valent anti-PV. Children with steroid dependent/resistant forms acquire high Ab levels, even if early relapses delay the tapering of steroids or if immunosuppressive agents are introduced. Patients who relapse during the tapering of steroids already have increased anti-pneumococcal Ab at the time of relapse.