Background

The introduction of PCV7 in August 2009 and PCV13 in May 2011 in The Gambia resulted in decline of invasive pneumococcal disease (IPD) incidence by 55% in the Eastern region although changing serotypes are emerging.

Methods

We retrospectively compared disease and serotype prevalence pre-PCV (January 2005-December 2009) and post-PCV (January 2012 - December 2015) periods for IPD in the Western region of the country

Results

Out of 12,454 blood and 979 CSF cultures analysed, 6.8% (847/12454) blood and 6.9% (68/979) CSF were clinically significant pathogens. The prevalence of IPD for suspected bacteraemia was 1.8% (218/12454) constituting 25.8% (218/846) of all confirmed cases and 3.9% (38/979) for meningitis constituting 55.9% (38/68). When compared by vaccine period, a significant drop across all age groups post-PCV was found, decreasing from 32.4% (160/494) to 16.5% (58/352) for bacteraemia and from 67.3% (33/49) to 26% (5/19) for meningitis.

Serotype data was available for 86.3% (221/256) and decrease in PCV13 vaccine serotypes from 62.2% (120/193) to 41.3% (26/63). Concurrently increase in non-vaccine serotypes from 24.9% (48/193) to 42.8 % (27/63) was found with 12F accounting for 50%.

Conclusions

The PCVs have reduced IPD but serotype replacement is noted warranting surveillance and more intervention.

Background

Pneumococcal carriage influences population-wide strain dynamics, but limited data exist on serotype-specific temporal carriage patterns among PCV-vaccinated West African infants.

Methods

Pneumococcus was cultured from nasopharyngeal swabs (n=1, 595) collected from 102 PCV7-exposed infants followed up from birth to 12 months. Serotyping was performed by whole genome sequencing and sweep-latex agglutination. Parametric survival models with constant hazard rates were fitted to estimate carriage dynamics (duration, clearance and acquisition).

Results

The infants were naturally colonised with 60 pneumococcal serotypes with a mean of 7 (range:2-11) serotypes per infant. Carriage dynamics estimates for serotypes 5, 7F, 39, 9A, and 12F are provided here for the first time in infants. There was no correlation between time to first acquisition and carriage duration (ρ=0.06, P=0.709). Serotype prevalence showed a weak correlation with initial acquisition (ρ=0.07, P=0.706), carriage duration (ρ=0.219, P=0.194), and reacquisition times (ρ=0.09, P=0.730). Onset of initial acquisition was longer than the time taken to reacquire serotypes (median: 136.23 vs 26.15 days, P=7.63×10-6). Overall, serotype-specific carriage durations after initial acquisition and reacquisition were significantly different (P=0.020), varying by serotype.

Conclusions

Pneumococcal carriage dynamics among Gambian infants are complex and highly variable by serotype which may have important implications for transmission and invasive disease.

Background

Serotype 2 was a major cause of pneumococcal pneumonia about 100 years ago and then disappeared. Recently, serotype 2 re-emerged in many countries, including Bangladesh and associated with meningitis. This study aims to understand genomic and epidemiological characteristics of newly emerged serotype 2 strains.

Methods

Whole-genome sequencing was performed on 146 isolates (invasive= 125, carriage= 8 and other= 5, unknown= 8) collected between 1989 and 2017. Data were analyzed for comparative genomics, antimicrobial resistance and molecular typing.

Results

Isolates were from 16 countries, mostly in Asia (n=93), Africa (n=23) and Oceania (n=26). Bangladesh (n=66) and Papua New Guinea (n=26) contributed 63% of the isolates. Among the known clinical conditions, 80% (91/113) were from meningitis. All isolates belonged to GPSC96 lineage and descended from two predominant sequence types: ST74 found in Asia and Africa, and ST1504 found in Papua New Guinea and Israel. Almost all isolates were sensitive to all antibiotics. No significant genetic differences were detected between invasive and carriage isolates.

Conclusions

Our findings don’t explain why the recent increase in serotype 2 occurred but exclude an outbreak or emergence of an antimicrobial-resistant strain as the cause. These isolates have unusually high propensity to be invasive, mostly causing meningitis.

Background

By 2015, pneumococcal conjugate vaccines (PCVs) had been introduced into the infant immunization programmes of most countries in West and Central Africa. We modelled the trends in meningitis cases and deaths among children before and after PCV introduction.

Methods

A total of 36,901 children under 5 years of age with suspected meningitis were enrolled at sentinel hospitals across 10 West and Central African countries between 2010 and 2016 through the Paediatric Bacterial Meningitis (PBM) Surveillance Network . To assess disease and mortality trends before and after PCV introduction, we applied interrupted time-series models and random effects meta-analysis.

Results

Across the sub-regions, there was a decline of 35% (95% CI 2-57%, p=0.04) in annual suspected meningitis cases and 26% (95% CI 3-44%, p=0.03) in laboratory confirmed meningitis in the post vs. pre-PCV period. Likewise, there was a decreased trend in mortality among suspected meningitis cases (33% decline, 95% CI -23-52%, p=0.27) post PCV introduction. There was considerable heterogeneity among countries with the larger and more precise reduction estimates in countries with >2 years post-PCV surveillance.

Conclusions

We observed significant declines in suspected and confirmed pediatric meningitis across the sub-regions following PCV implementation. Continued monitoring, particularly in countries with more recent PCV introduction is needed.

Background

Despite widespread use of PCV13, pneumococcal carriage remains high among Gambian infants. We investigated the role of biomass smoke exposure and inflammation in modulating pneumococcal carriage in The Gambia.

Methods

Rural Gambian children (n=120) were followed up at regular intervals from birth to two years of age. All infants received PCV13. Pneumococcal carriage was determined by quantitative PCR and inflammation by measuring plasma alpha-1 glycoprotein (AGP). Smoke exposure was self-reported by the mothers. Adjusted random effects regression models were applied to investigate the relationships between pneumococcal carriage, smoke exposure, and inflammation.

Results

Exposure to biomass smoke was significantly associated with a nearly 3-fold increase in the odds of pneumococcal carriage (OR 2.9, 95% CI: 1.13 - 7.5) and, in independent models, a 1/3-log10 increase in pneumococcal load (Coefficient 0.35, 95% CI: 0.11 - 0.59), compared to non-exposure. Inflammation (AGP) was significantly associated with an increased pneumococcal load (Coefficient 0.22, 95% CI: 0.03 - 0.41) in a model unadjusted for smoke exposure. Mediation analysis suggests that there are age, inflammation and smoke exposure interactions that may modify the effects of smoke exposure on pneumococcal carriage.

Conclusions

Biomass smoke exposure may be an important environmental factor driving pneumococcal carriage and loads among PCV-vaccinated Gambian children.