IMPACT OF PCV7/10/13 ON PREVALENCE OF PILIATED S. PNEUMONIAE STRAINS

Introduction: The Palestinian-Israeli Collaborative Research (PICR) was formed to investigate epidemiological studies while taking advantage of the unique setting provided. This study focuses on the pilus 1 carriage rate inof S. pneumoniae carriers shortly after the introduction of pneumococcal conjugate vaccines (PCV) in three distinct regions: Central Israel, East Jerusalem, and the Palestinian Authority. Central Israel and East Jerusalem follow the same vaccination program and are governed by the same Ministry of Health. However, the Palestinian Authority utilizes private clinics. PCV7 was introduced to central Israel and East Jerusalem in 2009, and later replaced by PCV 13 in late 2010. PCV10 was introduced to the Palestinian Authority in late 2011.

Methods: Data was collected from each region focusing on children less than 5.5 years old. Utilizing the design of a cross-sectional study, samples were taken during the years 2009, 2010, 2011, and 2014. Serotype prevalence, pilus 1 prevalence, and antibiotic resistance per region per year was identified through laboratory means.

Results: A total of 4500 children were screened from East Jerusalem (n=1267), Israel (n=819), and the Palestinian Authority (n=2414) during the years 2009, 2010, 2011, and 2014, while the overall rate of S. pneumoniae carriage remained approximately 30%. Pilus-1 carriage in East Jerusalem and the Palestinian Authority declined by approximately 7% from 2011 to 2014, however the frequency stayed within the typical range of Pilus-1 prevalence, while in Israel, a significant atypical decline was observed. Most of the Vaccine Types (VT) strains have diminished in Israel and East Jerusalem by 2014. While in the Palestinian Authority a decline is noted, VT serotypes are still present. Overall, a decrease of pilus 1 carriage and frequency of VT strains is observed in each region, as well as an increase in prevalence and piliation of Non-Vaccine Types (NVT) strains. Lastly, a higher rate of antibiotic non-susceptibility persists in S. pneumoniae strains that exhibit pilus-1 compared to S. pneumoniae strains that do not exhibit the gene.

Conclusions: The pneumococcal conjugate vaccine did indeed decrease the prevalence of VT strains in each region. However, pilus-1 was noticed to transfer from VT strains to NVT strains, preserving its typical carriage rate, save for Israel, which exemplifies a different story. There seems to exist an association between pilus-1 prevalence and frequency of specific strains, suggesting that pilus-1 confers an advantage for colonization and may be considered as a desirable vaccine candidate.