Frequency of Acute Otitis Media in Children Under 24 Months of Age Before and After the Introduction of the 10-valent Pneumococcal Conjugate Vaccine Into the National Immunization Program in Chile

Background:Streptococcus pneumoniae is the leading cause of acute otitis media (AOM). Ten-valent pneumococcal conjugated vaccine (PCV-10) was introduced to the Chilean National Immunization Program (NIP) in 2011. The aim of this study was to estimate the frequency of AOM in children <24 months of age attending the emergency department (ED) of Hospital Sotero del Rio (HSR) 4 years before and 4 years after the introduction of PCV-10 in the Chilean NIP. Methods: Register-based nested case-control study. Cases (n = 1907) were all children <24 months of age with a clinical diagnosis discharge of AOM at the ED of HSR, and controls (n = 244,334) were all other children <24 months of age attended at the same ED in the same time period, with any other discharge diagnosis. The data were obtained through HSR Statistical Service. Results: In the study period, there was a mean of 30,695 children <24 months managed each year at the ED of HSR. The percentage with AOM in the prevaccine period was 0.94% and in the postvaccine period was 0.62%, respectively (P = 0.026). Exposure to the PCV-10 was associated with a decreased risk to develop AOM in children <24 months, with an odds ratio of 0.659 (95% confidence interval: 0.60-0.72). Conclusions: Our study showed a significant decrease in the percentage and risk of AOM in children <24 months of age who visited the ED of HSR after implementation of PCV-10 in the NIP in Chile.