LAUSR

BACKGROUND Recently, emergence of a higher proportion of serotype 3 in children with parapneumonic pleural effusion/empyema (PPE/PE) were observed in Germany despite general immunization with 13-valent pneumococcal conjugate vaccine (PCV13) since 2009. The impact of PCV13 on the overall incidence of PPE/PE in children is unclear. METHODS Annual incidence of PPE/PE in children were determined using secondary health care data for 2009-2018, provided by the Barmer statutory health insurer, serving about 11% of the German population. Temporal trends of the annual incidence were modelled applying generalized additive models. RESULTS Overall incidence of PPE/PE in children ( ≤18 years) in the ten-year observation period was 18.17 per 100,000. The 0-1 year olds showed the highest incidence (43.09 per 100 000). PPE/PE incidence decreased from 2009 until 2013 (nadir 2013 was 15.36; 95% CI: 13.41-17.31). Since 2013, the data show an annual increase. The nadir of incidence for the 2-5 year olds (15.85; 95% CI: 11.27-20.43) and the 6-18 year olds (12.29; 95% CI: 10.23-14.36) was also in 2013, whereas for the 0-1 year olds it was found in 2014 (32.66; 95% CI: 23.79-41.54). The GAM across all age groups showed a nearly U-shaped curve between time and incidence of PPE/PE by calendar year (p-non-linear = 0.0017). The model confirms the nadir in the year 2013. DISCUSSION We found a nonlinear temporal trend of PPE/PE incidence in children with a decrease from 2009 to 2013 and a subsequent increase until 2018. The former might be explained by a quasi elimination of serotype 1, the latter by an increase in the proportion of serotype 3 as demonstrated in German surveillance data of pediatric PPE/PE cases generated during the same observation period.