Vaccines
The use of pneumococcal conjugate vaccines (PCVs) has reduced the frequency of AOM caused by Streptococcus pneumoniae. PCVs are not as effective against AOM as they are against invasive pneumococcal disease, but they still help a lot. However, because there are now at least 96 different serotypes of the pneumococcus based on different capsular types, we see a pattern of replacement of disease-causing strains by new strains within a few years of introduction of a new formulation. We started with 7 serotypes (Prevnar 7) in year 2000, and it was replaced by the current formulation with 13 serotypes (Prevnar 13) in 2010. Replacements have occurred again so vaccine companies are making new formulations for the future that include more serotypes, up to 20 serotypes. But, technically and feasibility-wise there is a limit to making such vaccines. A vaccine based on killed unencapsulated bacteria has been tested for safety and immunogenicity in young children. There is no test so far for prevention of AOM. Another type of vaccine based on proteins expressed by the pneumococcus that could be vaccine targets was tested in American Navajo children, and it failed to be as efficacious as hoped.
Dr. Michael E. Pichichero
Biomarkers.
Due to recurrent AOM or persistent otitis media with effusion, about 15% of children in the United States receive tympanostomy tubes. Among those who receive tubes, about 20% go on to receive a second set of tubes, often with adenotonsillectomy. To find a biomarker that could identify children likely to require a second set of tubes, the fluid in the middle ear was tested when a first set of tubes were inserted. If bacteria were detected by polymerase chain reaction (PCR) testing or if a profile of specific inflammatory cytokines was measured, those results could be used to predict a high likelihood for a second set of tubes.
Overdiagnosis
Diagnosis of AOM is challenging in young children, in whom it most frequently occurs. The ear canal is typically about 3 mm wide, the child struggles during the examination, and diagnostic skills are not taught in training, resulting in a high overdiagnosis rate. I presented data that suggest too many children who are not truly otitis prone have been classified as otitis prone based on incorrect clinical diagnosis. My colleagues and I found that 30% of children reach the threshold of three episodes of AOM in 6 months or four within a year when diagnosed by community pediatricians, similar to many other studies. Validated otoscopists (trained by experts with diagnosis definitively proven as at least 85% accurate using tympanocentesis) classify 15% of children as otitis prone – half as many. If tympanocentesis is used to prove middle ear fluid has bacterial pathogens (about 95% yield a bacterial otopathogen using culture and PCR), then about 10% of children are classified as otitis prone – one-third as many. This suggests that children clinically diagnosed by community-based pediatricians are overdiagnosed with AOM, perhaps three times more often than true. And that leads to overuse of antibiotics and referrals for tympanostomy tube surgery more often than should occur. So we need to improve diagnostic methods beyond otoscopy. New types of imaging for the eardrum and middle ear using novel technologies are in early clinical trials.