Predominance of nontypeable Haemophilus influenzae in children with otitis media following introduction of a 3+0 pneumococcal conjugate vaccine schedule.

In Australia the 7-valent pneumococcal conjugate vaccine (PCV7) is administered at 2, 4 and 6 months of age, with no booster dose. Information on bacterial carriage and the aetiology of recurrent acute otitis media (rAOM) after introduction of PCV7 using the 3+0 schedule is required to evaluate the potential impact of second generation pneumococcal vaccines. We found that 2-4 years after introduction of PCV7 in the National Immunisation Program, nontypeable Haemophilus influenzae (NTHi) was the predominant pathogen isolated from the nasopharynx and middle ear of children with a history of rAOM. Compared with healthy controls (n=81), NTHi and Streptococcus pneumoniae carriage rates were significantly higher in children with a history of rAOM (n=186) (19% vs. 56% p<0.0001 and 26% vs. 41%, p=0.02, respectively). Carriage of PCV7 pneumococcal serotypes was rare, whereas PCV7-related and non-PCV7 serotypes were isolated of 38% of cases and 24% of controls. Serotype 19A was the most common serotype isolated from the nasopharynx and middle ear and accounted for 36% (14/39) of total pneumococcal isolates with reduced susceptibility to cotrimoxazole. Of the 119 children carrying NTHi, 17% of isolates were β-lactamase positive. The scarcity of PCV7 serotypes in children with and without a history of rAOM indicates that the 3+0 PCV7 schedule is preventing carriage and rAOM from PCV7 serotypes. Introduction of new vaccines in Australia with increased pneumococcal serotype and pathogen coverage, including 19A and NTHi, should decrease the circulation of antibiotic-resistant bacteria and reduce the burden of rAOM.