BACKGROUND: This study was undertaken to ascertain Haemophilus influenzae type b (Hib) conjugate vaccination status following discharge from hospital and to determine the time taken to vaccinate with Hib conjugate vaccine following hospital discharge of unvaccinated children. MATERIALS AND METHODS: Population-based cross-sectional survey involving children aged 3-59 months admitted to a hospital with laboratory confirmed invasive H. influenzae disease. RESULTS: Of 51 eligible children, 42 (82%) had not received Hib conjugate vaccine prior to admission. No children were immunized prior to discharge. Vaccination following discharge took an average of 110 days (range 3-441 days). More than one quarter (28%) remained unvaccinated following discharge. If these children had been immunized, immunization coverage among this group of children would have increased significantly from 73% to 98% (p = 0.0017). CONCLUSION: In the immediate post-Hib conjugate vaccine period, delayed immunization after discharge was identified. This reduces the individual and community benefits of immunization.