Complicated otitis media (OM) is a common paediatric problem and includes two major entities: persistent acute OM (AOM) and recurrent AOM (R-AOM). Double-tympanocentesis studies comparing the microbiology of initial and recurrent episodes of AOM have demonstrated that most recurrent episodes occurring within 1 month after antibiotic therapy are new infections, not true bacteriological relapses. These findings have highlighted the importance of bacteriological eradication in the prevention of subsequent R-AOM episodes. The seven-valent pneumococcal conjugate vaccine (PCV7) targets Streptococcus pneumoniae, one of the main AOM pathogens, and data on the impact of PCV7 on complications of AOM, such as mastoiditis, are presented.