EPIDEMIOLOGY OF INVASIVE PNEUMOCOCCAL INFECTIONS IN INFANTS AND YOUNG-CHILDREN IN METROPOLITAN SANTIAGO, CHILE, A NEWLY INDUSTRIALIZING COUNTRY

Aim. To study the epidemiology of invasive pneumococcal infections in infants and young children in Santiago, Chile, as a representative ped iatric population in a newly industrializing country where pneumococca l conjugate vaccines may be used in the future. Methods. A 5-year retr ospective laboratory-based review (1989 to 1993) was followed by a S-y ear prospective laboratory and hospital surveillance study in two of t he six health administrative areas of Santiago to detect all hospitali zed cases of invasive pneumococcal disease (defined as Streptococcus p neumoniae isolated from blood, cerebrospinal fluid or another normally sterile site) among infants and children (0 to 23 months of age in th e retrospective and 0 to 59 months of age in the prospective study). R esults, During the B-year retrospective survey the incidence of invasi ve pneumococcal disease was 90.6 cases per 10(5) infants 0 to 11 month s old and 18.5 cases per 10(5) toddlers 12 to 23 months old. Similar r ates (60.2 per 10(5) infants and 18.1 per 10(5) toddlers) were recorde d during the 3 years of prospective surveillance. Among the 110 cases in children 0 to 59 months of age detected during the 3-year prospecti ve surveillance, 2 clinical forms, pneumonia and meningitis, accounted for 87.2% of all cases; 13 of the 49 pneumonia patients (26%) had emp yema as a complication, Notably 40 of the 110 cases (36.4%) occurred b efore 6 months of age (63.4% of the 63 infant cases). Serotypes 1, 14, 5 and 6B were the most prevalent. Overall 76 and 69%, respectively, o f S. pneumoniae isolates were antigenic types that would be covered by the 11- or 9-valent conjugate vaccines under development. Conclusions , Invasive pneumococcal infections in Santiago, Chile, exhibit an epid emiologic pattern intermediate between that of developing and industri alized countries, The high burden of disease in early infancy dictates that an accelerated immunization schedule (beginning in the perinatal period) or maternal immunization with pneumococcal vaccines should be explored.