[Impact of the 13-valent pneumococcal conjugate vaccine on the incidence of consolidated pneumonia in children younger than 5 years old in Pilar, Buenos Aires: A population-based study].

INTRODUCTION In January 2012, Argentina introduced the 13-valent pneumococcal conjugate vaccine (PCV13) in its immunization schedule for children younger than 2 years old. Coverage in Pilar in 2012 reached>90% for the first two doses and 60% for the third dose. OBJECTIVE To measure the effectiveness of PCV13 to reduce the incidence of consolidated pneumonia (CP)in the two-year period following its introduction in the immunization schedule. METHODS Prospective, population-based study conducted in Pilar. All children younger than 5 year sold with clinical signs of pneumonia assisted at the reference hospitals (both inpatients and outpatients) in the first two years since the vaccine introduction (2012-2013) were included. The annual incidence of CP was compared to the 2003-2005 baseline period. Clinical and radiological assessments were done as per the World Health Organization's criteria. RESULTS Six hundred and sixty-six patients with clinical suspicion of pneumonia were included. CP was diagnosed in 309 patients; 52.1% were girls, 70.2% were younger than 2 years old, and 56.4% had been immunized with the PCV13; 4.5% (14/309) had bacteriological confirmation (S. pneumoniae: 4; N. meningitidis: 4; S. aureus: 2; others: 4). A significant reduction in the incidence of CP (per 100 000 children younger than 5 years old) was observed between the pre- and postimmunization periods, from 750 (204/27209) to 561 (171/30 475) in 2012 and to 453 (138/30 475) in 2013; effectiveness accounted for 25.2% and 39.6%, respectively. Reduction in infants younger than 1 year old: 33.9% in 2012 and 44.6% in 2013; and in children aged 12-23 months old: 57.9% in 2013. No significant differences were observed in the incidence of CP at an older age. CONCLUSIONS Following the introduction of PCV13 in Argentina's immunization schedule, a fast and significant reduction in the incidence of CP was observed, mainly in infants younger than 1 year old in 2012 and in children younger than 2 years old in 2013.