SEROTYPE DISTRIBUTION IN INVASIVE PNEUMOCOCCAL DISEASE BEFORE AND AFTER INTRODUCTION OF PCV10 IN CHILDHOOD VACCINATION IN ICELAND
Iceland introduced PCV10 in 2011. The aim of this study was to monitor pneumococcal serotype distribution and antimicrobial resistance in invasive pneumococcal disease (IPD) eight years before (2004-2011; PreVac) and after vaccination (2012-2019; PostVac).
All IPD samples (blood, cerebrospinal fluid and joint fluid) were recorded at the reference laboratory, Landspitali University Hospital. All isolates were serotyped with Immulex Pool Antisera and/or multiplex PCR.
In total, 564 IPD cases were detected, thereof 75 cases PreVac and 15 PostVac from children (<18y) and PCV10 serotypes were 82.7% and 13.3%, respectively (p<0.001). In children <2 years, 55 IPD cases were recorded PreVac and six PostVac (three of serotype 19A and one of each 14, 22F and 23A).
In adults, 270 cases were detected PreVac and 204 PostVac, thereof PCV10 serotypes 63.7% and 23.0%, respectively (p<0.001). The most common non-PCV10 serotypes in adults PostVac were 19A (12.3%), 22F (11.3%), 9N (7.4%) and 3 (6.4%).
Penicillin non-susceptible pneumococci (PNSP) Pre- and PostVac were 29/345 (8.4%) and 30/219 (13.7%), respectively (p=0.036). The most common PNSPs PostVac were 19A (23.3%), 15A (16.7%), 6C (13.3%) and 35B (10.0%).
PCV10 impact was greatest among children <2 years. The increasing prevalence of penicillin non-susceptible pneumococci of non-PCV10 serotypes is concerning.