Anthony Scott, Kenya
Author Of 3 Presentations
PNEUMOCOCCAL CONJUGATE VACCINE DOSE-RANGING STUDIES IN HUMANS: A SYSTEMATIC REVIEW (ID 268)
Abstract
Background
Reduced dose vaccination with pneumococcal conjugate vaccines may protect against infection. We sought to examine the relationship between the dose of polysaccharide in conjugate vaccines (PCVs) and immunogenicity.
Methods
A systematic review of English publications that evaluated variable dose immunogenicity of PCVs in humans was performed in Medline and Embase databases (Ovid SP) in August 2019. Results were synthesised descriptively due to the heterogeneity of product valency, content and vaccine schedule.
Results
We identified 1691 articles after de-duplication; 9 studies met our inclusion criteria; 2 in adults, 6 in children and 1 in both. Doses of polysaccharide evaluated ranged from 0.44 mcg to 17.6 mcg. Thirty days after vaccination following a single dose or 2p+1 schedule, all doses tested in infants achieved mean IgG concentrations (GMCs) above the acceptable correlate of protection (COP; 0.35 mcg) and only three GMCs' 95% confidence intervals crossed the COP. All doses tested in adults achieved GMCs that were comparable to those considered protective in children who have received 3 standard vaccine doses.
Conclusions
For some products, the mean antibody concentrations induced for some pneumococcal serotypes increased with increasing doses of the polysaccharide but the functional significance of these is uncertain.
GENOMIC ANALYSES OF BACTERIOCINS IN ICELANDIC AND KENYAN PNEUMOCOCCI COLLECTED BEFORE AND AFTER PCV10 INTRODUCTION (ID 503)
- Madeleine E. Butler, United Kingdom
- Melissa J. Jansen van Rensburg, United Kingdom
- Asma Akter,
- Calum Forrest,
- Andries J. Van Tonder,
- Sigridur Quirk,
- Gunnsteinn Haraldsson, Iceland
- Stephen D. Bentley, United Kingdom
- Angela M. Karani, Kenya
- Helga Erlendsdottir, Iceland
- Asgeir Haraldsson, Iceland
- Karl G. Kristinsson, Iceland
- Anthony Scott, Kenya
- Angela Brueggemann, United Kingdom
Abstract
Background
Widespread use of pneumococcal conjugate vaccines (PCVs) perturb the bacterial population structure, the consequences of which include changes in nasopharyngeal competition among pneumococci. Bacteriocins are antimicrobial peptides produced by bacteria, and are believed to inhibit competing bacterial strains. Twenty putative pneumococcal bacteriocins have been identified: this study aims to compare the bacteriocin distribution among pneumococci recovered pre- and post-PCV10 introduction in two countries.
Methods
Carriage and disease pneumococci collected in Iceland (n=1,916) and Kenya (n=3,257) before and after PCV10 introduction were sequenced and genomes were screened for twenty different bacteriocin sequences. Significant changes in the prevalence of genetic lineages, serotypes, and bacteriocins post-PCV10 introduction were assessed.
Results
PCV10 use led to a significant reduction in the prevalence of vaccine serotypes and associated genetic lineages in both countries. Overall, 18 of 20 bacteriocins were detected in 1% to 100% of genomes. The prevalence of six bacteriocins was significantly altered in the Kenyan dataset post-PCV10, and three of these also changed in the Icelandic dataset. These bacteriocins were associated with genetic lineages that also significantly changed in prevalence.
Conclusions
The bacteriocin distribution changed significantly following PCV10 introduction in Iceland and Kenya. The biological relevance of these changes to competition dynamics is currently under investigation.
LONG-TERM TRENDS IN NASOPHARYNGEAL CARRIAGE OF VACCINE-TYPE PNEUMOCOCCI: FINDINGS FROM A MATURE 10-VALENT PNEUMOCOCCAL CONJUGATE VACCINE (PCV10) PROGRAM IN KENYA (ID 966)
Abstract
Background
PCV10 was introduced into Kenya’s immunization program in 2011, with catchup in children aged 1-4 years. We evaluated the long-term effect of PCV10 on nasopharyngeal carriage of Streptococcus pneumoniae serotypes included in PCV10.
Methods
Population-based annual cross-sectional nasopharyngeal carriage surveys were conducted in randomly selected individuals between 2009 and 2019 (N= ~1000 in 2019; N= ~500 in all others) in Kilifi, Kenya. Pneumococcal identification was performed per WHO standards. Annual vaccine-type carriage prevalence was modelled using log-binomial regression with a curved function for year and adjustment for age-specific sampling probability.
Results
Compared to 2010, carriage of PCV10-type pneumococci declined significantly through 2019 in children aged <5 years to 6.1% (adjusted prevalence ratio 0.18, 95%CI 0.11-0.30) but not in children aged 5-14 years (prevalence= 7.1%; 0.71, 0.38-1.34) nor adults ≥15 years (prevalence= 1.0%; 0.49, 0.17-1.35). PCV10-type carriage was significantly lower in 2017 compared to 2010 for all age groups and did not differ from carriage prevalence in 2019 (figure).
Conclusions
PCV10-type carriage prevalence appears to be approaching equilibrium, yet residual carriage persists. Virtual elimination of PCV10-type carriage (≤1% in children <5 years; ≤3% in children 5-9 years) – a prerequisite for introduction of reduced dose schedules – is unlikely without implementation of additional strategies.