2699. Pneumococcal Vaccination During Chemotherapy in Children Treated for Acute Lymphoblastic Leukemia

BACKGROUND: Children undergoing therapy for acute lymphoblastic leukemia (ALL) are at high risk of invasive pneumococcal disease (IPD). Immunization with conjugated vaccines following chemotherapy is recommended for pediatric patients. In an attempt to provide an earlier protection against invasive pneumococcal infection, we aimed to assess immunity to S. pneumoniae among children vaccinated during chemotherapy for ALL. METHODS: We retrospectively analyzed the rate of seroprotection among ALL children treated in our institution in accordance with the DFCI ALL Consortium protocol between 2007 and 2014. A pneumococcal conjugate vaccine (PCV) booster was given to all subjects after the end of chemotherapy (groups 1 and 2). In group 2, a PCV dose was also administered during the maintenance phase. Clinical characteristics as well as individual immunization records were collected from our local immunization database. All children were up to date with their vaccination schedule at diagnosis. Serum samples were obtained on a routine follow-up visit, after the end of chemotherapy and after the PCV vaccine booster to measure serotype-specific IgG pneumococcal antibodies. Antibody level ≥0.35µg/mL was considered protective. Patients with seroprotective antibodies level for ≥ 50% of serotypes contained in vaccines were defined as seroprotected. RESULTS: 62 children [34 girls (54.8%)] were included in the analysis. Median age at diagnosis was 45 months (range:12–160). At the end of chemotherapy, 34.2% of children in group 1 (13/38) and 79.2% in group 2 (19/24) were seroprotected (P < 0.01). Median interval of time between the end of chemotherapy and the PCV booster vaccination was 6 months (range: 2–64 months). After PCV-13 booster, the rate of seroprotection raised to 100% (38/38) in group 1 and 91.7% in group 2 (22/24). CONCLUSION: Rates of pneumococcal seroprotected children treated for ALL are low at the end of chemotherapy. However, PCV booster during chemotherapy could be useful to increase the level of seroprotection and shorten the period of susceptibility to IPD. After chemotherapy for ALL, children benefit from a PCV booster to enhance seroprotection. [Image: see text] DISCLOSURES: All authors: No reported disclosures.