The changes of prevalence and etiology of pediatric pneumonia from National Emergency Department Information System in Korea, between 2007 and 2014

Shin, Eun Ju; Kim, Yunsun; Jeong, Jin-Young; Jung, Yu Mi; Lee, Mi-Hee; Chung, Eun Hee

Seven-valent PCV (PCV7) was developed in 2000 and universally used to effectively prevent S. pneumonia, a major pathogen for severe invasive bacterial diseases in addition to pneumonia, in children under the age of 2 years. 15, 16) The efficacy of the PCV7 for preventing invasive infections and acquiring herd immunity has been confirmed in several studies, including through monitoring by the US Centers for Disease Control. 15, 17) The PCV has been associated with a >25% decrease in streptococcal pneumonia, as well as lowering the risk of invasive pneumococcal disease and of pneumonia caused by antibiotics-resistant pneumococcal strain. 15) In Korea, the increasing trend in deep infection caused by one of the subtypes of S. pneumoniae in children under the age of 5 years from 1991 to 2003 was reversed in 2004 to 2006, presumably due to PCV immunization programs implemented in November 2003. 18) Our data indicates the presence of a herd immunity among unvaccinated individuals, with a decrease in the prevalence of bacterial and pneumococcal pneumonia among children 7 to 18 years of age, although the PCV7 optional immunization program was only introduced in Korea in November 2003. 19) MP usually affects preschool-and school-aged children, with a cyclical epidemic occurring every 3 to 4 years in Korea. 8, 10) According to an epidemiological survey conducted by the Korea National Research Institute of Health, the incidence of mycoplasma infection increased in 2007, with a subsequent upsurge between 2010 and 2011. 9) MP is associated with diverse radiological findings, including concomitant pleural effusion and lobar pneumonia, which makes its differential diagnosis from bacterial pneumonia difficult merely based on clinical presentations and chest radiographs. 20, 21) Further, it is not uncommon for M. pneumoniae infection to coexist with infections from other pathogens. 22) Therefore, the prevalence and effects of a M. pneumoniae infection should be considered whenever the prevalence of bacterial pneumonia is evaluated. Over our 8-year study period, although not significant, though, the prevalence of bacterial pneumonia decreased between 2007 and 2014, with the exception of a unique spike in 2011. The increase in the total number of patients with pneumonia, the number of patients with bacterial pneumonia, the number of patients with pleural effusion and empyema in 2011 and the prevalence of bacterial pneumonia among children in the 4-6 and 7-12 years age groups in 2011 are speculated to have resulted from an nationwide MP epidemic extending from late 2010 to early 2012 (Fig. 2) . The increased prevalence three years later (2013-2014) also likely resulted from a MP epidemic.