Background: Acute otitis media is among the most common reasons young children seek medical care, with Streptococcus pneumoniae the most common pathogen. Despite introduction of heptavalent pneumococcal conjugate vaccine (PCV7) in 2000, recent experience suggests an increase in complications of acute otitis media, particularly acute mastoiditis.
Methods: We performed a retrospective review of acute mastoiditis in children from 1999 to 2008 using inpatient data from the Colorado Hospital Association and the Children's Hospital Colorado. The study included patients with documentation of acute mastoiditis or mastoidectomy and excluded those with chronic mastoiditis, chronic otitis media or cholesteatoma.
Results: The annual incidence of acute mastoiditis in children <2 years/100,000 population was 11.0 in 2001 before decreasing to 4.6 in 2002 and 4.5 in 2003. The incidence then increased to 12.0 in 2008 (total N = 242). The proportion of S. pneumoniae isolates nonsusceptible to penicillin increased from 0% (0/16) between 1999 and 2004 to 38% (5/13) between 2005 and 2008 (P = 0.03).
Conclusions: The incidence of acute mastoiditis in Colorado children <2 years of age exhibited a dynamic pattern from 1999 to 2008: a significant decline early after introduction of PCV7 that paralleled initial vaccine uptake, followed by an increase in subsequent years to pre-PCV7 levels. Replacement with non-PCV7 pneumococcal serotypes and increased pneumococcal antibiotic resistance may be responsible for the increase in incidence to pre-PCV7 rates. Surveillance of mastoiditis incidence, pathogen distribution and resistance patterns following introduction of 13-valent PCV is warranted.