Studying PCV impact on clinical presentation of otitis media helps to understand its pathogenesis

Complex otitis media (OM) may present with intact tympanic membrane or spontaneous otorrhea. We compared dynamics of intact tympanic membrane and spontaneous otorrhea OM following 7- and 13-valent conjugated vaccines (PCV7, PCV13) implementation, since differences in dynamics may imply different underlying mechanisms.

A prospective, population-based, active surveillance. Episodes with middle-ear fluid cultures in children < 3 years were included. Defined sub-periods were: pre-pneumococcal conjugated vaccines (PCV) (2004-2008); PCV7 (2009-2011); PCV13 (2014-2016).

Of 7705 episodes, 57.2% had intact tympanic membrane, 16.8% spontaneous otorrhea, 26.0% unknown. In the pre-PCV period, the spontaneous otorrhea group was older and had higher proportions of factors associated with recurrence/chronicity. During the PCV7 period, spontaneous otorrhea and intact tympanic membrane episodes caused by PCV13 serotypes decreased significantly (43% and 51%, respectively) and those caused by non-PCV13 serotypes and culture-negative episodes increased significantly. However, rates increases were steeper in the spontaneous otorrhea group for both non-PCV13 serotypes (117% vs. 38%) and culture-negative (720% vs. 69%). In the spontaneous otorrhea group, nontypeable Haemophilus influenzae rates increased non-significantly by 10% and all-cause OM rates increased significantly by 56%, while in the intact tympanic membrane group the respective rates decreased significantly by 22% and 11%. These trends were especially pronounced in ages 24-35 months. Despite these differences, after PCV13 introduction, both spontaneous otorrhea and intact tympanic membrane rates declined for all outcomes.

Spontaneous otorrhea was associated with older age, frequent history of complex OM and delayed PCV impact, suggesting a higher proportion of advanced-stage complex OM.