Invasive Streptococcus Pneumoniae Infections in Pediatric Cancer Patients: High Morbidity and Mortality with Several Vaccine Failures.

Invasive pneumococcal infections can be devastating in the setting of immune deficiency. These infections have been seen in pediatric oncology practices, but the outcome has not been reported. With the introduction of routine 7- valent pneumococcal conjugate vaccine (PCV7) the rate of pneumococcal infections dramatically decreased in the general pediatric population. It is unclear if a similar reduction in rate would be seen in pediatric oncology patients. A total of 44 pneumococcal infections occurred in 34 oncology patients at Childrens Hospital and Clinics of Minnesota over a 5-year period (5/1/2001 – 4/30/2006). Twenty-five episodes of invasive infection were identified in 24 patients, of which 4 (16.7%) required intensive care admissions and 2 of them died (8.3%). During this period 863 new malignancies were diagnosed, therefore our rate of invasive infection is estimated to be 28 per 1000 oncology patients. This is higher than the reported rate of 3.8 8.1 infections per 1000 stem cell transplantation patients. Fifteen patients (62%) with invasive infections were diagnosed with leukemia, of which 12 had acute lymphoblastic leukemia. The invasive infections occurred a median of 15.2 months (range 0–36) after diagnosis and the median patient age at time of infection was 5.6 years (range 1.5 - 14). The average length of hospitalization for patients was 8.3 days (range 0–38), with six patients receiving outpatient therapy alone. Pneumococcal serotypes were known in 21 of the 25 episodes of invasive pneumococcal infection and in 1 non-invasive infection. Of the 22 serotypes identified, 19 were covered by either PCV7 or the 23-valent pneumococcal polysaccharide vaccine (PS23). Eleven patients who were immunized with either PCV7 or PS23 later developed a pneumococcal strain that should have been covered by the immunization. Three patients who received immunization acquired a strain of streptococcus pneumoniae not included in either vaccine. Invasive pneumococcal infection is a potentially preventable complication with a high morbidity and mortality. Use of PCV7 or PS23 may not prevent the development of pneumococcal infection in pediatric oncology patients with vaccine-susceptible strains. It is unclear whether immunization before and during the immunocompromised period results in protective immunity against streptococcus pneumoniae.