Recurrent invasive pneumococcal disease in children: epidemiological, microbiological, and clinical aspects from a Danish 33-year nationwide survey (1980-2013).

Background: Pneumococcal diseases play a major role in human morbidity and mortality. We present the results of a Danish nationwide study of recurrent paediatric invasive pneumococcal disease (rIPD) focusing on the epidemiological, microbiological, and clinical aspects. Methods: All laboratory-confirmed cases of IPD in children aged 0-15 y were identified from the Neisseria and Streptococcus Reference Laboratory, Statens Serum Institut, Denmark for the period 1980-2013. rIPD was defined as isolation of Streptococcus pneumoniae from any normally sterile site >= 30 days after an initial positive culture. Clinical data were obtained for all children with rIPD. Results: Of all children with IPD, 2.4% (59/2418) experienced at least 1 episode of rIPD, and an underlying condition was documented in 39 (66%). Immune deficiency due to transplantation (n = 9) was the most common disease; however, anatomic abnormalities (n = 8), complement C2 deficiency (n = 4), and congenital asplenia (n = 3) were all registered more than once. No underlying disease was detected in 18 children (31%). Based on the serotype distribution of S. pneumoniae isolates in rIPD among children aged 0-5 y (n = 41), 51%, 66%, and 78% of the cases would have been covered by the 7-, 10-, and 13-valent pneumococcal conjugate vaccines, respectively. Conclusions: Of children with an IPD episode, 2.4% experienced rIPD, and an underlying disease was documented in 66% of these children. Investigation of underlying conditions is essential in episodes of rIPD.