Epidemiology of acute otitis media in children after introduction of the 13-valent pneumococcal conjugate vaccine

Thirteen-valent pneumococcal conjugate vaccine (PCV13) is now widely used in many countries. Widespread use of the vaccine, which has been dramatically effective, has changed the epidemiology of pneumococcal infection. Streptococcus pneumoniae is one of the causative pathogens of acute otitis media (AOM), and its change may influence both the clinical features and treatment of this disease. We conducted a nationwide survey in Japan from July 2016 to March 2017 to elucidate the current epidemiologic profile of AOM after the introduction of PCV13. We analyzed the bacterial pathogens, pneumococcal serotypes, and patient background factors in 529 children with AOM (97% of them had received at least 1 PCV dose). The most frequently detected bacterial pathogen was Haemophilus influenzae (57%), followed by Streptococcus pneumoniae (26%), Staphylococcus aureus (8%), Group A streptococcus (3%), and Moraxella catarrhalis (1%). For the case of Streptococcus pneumoniae, the most frequent serotype was 15A (15%), followed by 35B (12%), 3 (11%), 10 A (9%), and 15B (9%), indicating that the frequency of the PCV13 serotypes had decreased to 16%. In regard to the patient background factors, 61% were aged less than 2 years, 81% had severe AOM, 45% had experienced recurrent or/and protracted otitis media, 72% attended day-care centers, and 55% had associated rhinosinusitis. Antibacterial agents recommended by the Clinical Practice Guidelines for Diagnosis and Management of AOM in Children in Japan were administered to 97% of the patients, and the cure rate of first-line treatment was approximately 67%. With the widespread use of PCV13 in Japan, Haemophilus influenzae has become the predominant causative pathogen of AOM, although there have been no apparent changes of the patient background factors or efficacy of treatment. When treating AOM today, it is important to select therapy in the conventional way, i.e., based on the patient background factors and drug susceptibility profile of the causative pathogens, keeping in mind that Haemophilus influenzae has become the predominant causative pathogen.