This is a literature report from a medical journal. This author reported similar events for four patients. This is the fourth of four reports. The authors report a cluster of cases of IPD (invasive pneumococcal disease) in previously healthy vaccinated children. After observing a cluster of IPD cases among children hospitalized at the authors' hospital queried the institution's database for children under the age of 18 years who presented during 2014 with positive blood, cerebrospinal fluid, or pleural fluid cultures. The authors abstracted demographic, clinical, and microbiological information including pneumococcal serotypes from the medical records. The institutional Review Board approved the study. Five previously healthy children without identifiable comorbidities or suspected immunodeficiencies were diagnosed with IPD between 26Oct2014 and 19Nov2014 based on culture results. Their cultures were forwarded to the hospital for subsequent serotyping. The average age of patients within this cluster was 3.64 years (0.62-5.58 years). Three patients were male. Four children had previously received appropriate immunizations with PCV-13. Three children were found to have serotype 19A (one of whole was unvaccinated, secondary to parental decision) and one child was found to have serotype 4. Both 19A and 4 were included in the PCV-13. The fifth child had serotype 17F, which was not included in PCV-13. S. pneumoniae was isolated from peripheral blood cultures in all cases. Four children presented with pneumonia, confirmed by consolidation on chest X-ray, and one presented with a unilateral infection involving the skin around the eye (preseptal cellulitis). All five pneumococcal isolates were susceptible to beta-lactams and macrolides. Children with bacteremic pneumonia were treated initially with either ampicillin (n=2) for 1-2 days, followed by amoxicillin for a total course of treatment of 10-14 days, respectively, or ceftriaxone (n=2, one of whom had a non-anaphylactic allergy to penicillin), for 1-2 days, followed by amoxicillin or cefpodoxime for 10-14 days, respectively. The patient with preseptal cellulitis received one dose of ampicillin/sulbactam followed with standard dose amoxicillin/clavulanate for 10 days. The patients recovered without complications, except for one child with serotype 4 pneumococcal pneumonia. This child developed empyema after discharge, but was successfully treated with video-assisted thoracoscopy and amoxicillin therapy. The authors report a cluster of IPD among five previously healthy children who presented in 2014. Four of these children had been appropriately vaccinated with PCV-13, therefore these cases represent breakthrough pneumococcal infections. Only one of these patients had a serotype that was not covered by the vaccine. This case refers to a child patient of an unspecified age, ethnicity and gender who received PCV-13 (unknown manufacturer) via an unspecified route of administration, on an unspecified date, at single dose. The patient experienced breakthrough pneumococcal infection, serotype 17F on an unspecified date with outcome of recovered. The patient underwent lab tests and procedures which included susceptibility test: susceptible to beta-lactams and macrolides, peripheral blood culture which detected S. pneumoniae, serotyping: serotype 17F and chest X-ray. Therapeutic measures were taken as a result of the event. Pfizer is the Marketing Authorization Holder of PCV-13 in the reporter's country. This may be a duplicate report if another Marketing Authorization Holder of PCV-13 has submitted the same report to the regulatory authorities.