Biology subjects

Tabu, C.

Publications and source records attributed to Tabu, C..

3 recordsLinked to original sources

bioRxiv2018

Coverage and timeliness of vaccination and the validity of routine estimates: Insights from a Vaccine Registry in Kenya

The benefits of childhood vaccines are critically dependent on vaccination coverage. We used a vaccine registry (as gold standard) in Kenya to quantify errors in routine coverage methods (surveys and administrative reports), to estimate the magnitude of survivor bias, contrast coverage with timeliness and use both measures to estimate population immunity.\n\nWe found coverage surveys in the 2nd year of life overestimate coverage by 2%. Compared to mean coverage in infants, static coverage at 12 months was exaggerated by 7-8% for third doses of oral polio, pentavalent (Penta3) and pneumococcal conjugate vaccines, and by 24% for the measles vaccine. Surveys and administrative coverage also underestimated the proportion of the fully immunised child by 10-14%. For BCG, Penta3 and measles, timeliness was 23-44% higher in children born in a health facility but 20-37% lower in those who first attended during vaccine stock outs.\n\nCoverage surveys in 12-23 month old children overestimate protection by ignoring timeliness, and survivor and recall biases.

epidemiology↗

bioRxiv2018

The merits of sustaining pneumococcal vaccination after transitioning from Gavi support - a modelling and cost-effectiveness study for Kenya

IntroductionMany low income countries soon will need to consider whether to continue pneumococcal conjugate vaccine (PCV) use at full costs as they transition from Gavi support. Using Kenya as a case study we assessed the incremental cost-effectiveness of continuing PCV use.\n\nMethodsWe fitted a dynamic compartmental model of pneumococcal carriage to annual carriage prevalence surveys and invasive pneumococcal disease (IPD) incidence in Kilifi, Kenya, and predicted disease incidence and related mortality for either continuing PCV use beyond 2022, the start of Kenyas transition from Gavi support, or its discontinuation. We calculated the costs per disability-adjusted-life-year (DALY) averted and associated prediction intervals (PI).\n\nResultsWe predicted that overall IPD incidence will increase by 93% (PI: 72% - 114%) from 8.5 in 2022 to 16.2 per 100,000 per year in 2032, if PCV use is discontinued. Continuing vaccination would prevent 15,355 (PI: 10,196-21,125) deaths and 112,050 (PI: 79,620- 130,981) disease cases during that time. Continuing PCV after 2022 will require an estimated additional US$15.6 million annually compared to discontinuing vaccination. The incremental cost per DALY averted of continuing PCV was predicted at $142 (PI: 85 - 252) in 2032.\n\nConclusionContinuing PCV use is essential to sustain its health gains. Based on the Kenyan GDP per capita of $1445, and in comparison to other vaccines, continued PCV use at full costs is cost-effective. These arguments support an expansion of the vaccine budget, however, affordability may be a concern.\n\nFundingFunded by the Wellcome Trust.

epidemiology↗

bioRxiv2018

Impact of 10-valent pneumococcal conjugate vaccine on invasive pneumococcal disease and nasopharyngeal carriage in Kenya

Background10-valent pneumococcal conjugate vaccine (PCV10), delivered at 6, 10 and 14 weeks of age, was introduced in Kenya in January 2011, accompanied by a catch-up campaign in Kilifi County for children <5 years. Coverage with [≥]2 PCV10 doses in children 2-11 months was 80% in 2011 and 84% in 2016; coverage with [≥]1 dose in children 12-59 months was 66% and 87%, respectively.\n\nMethodsClinical and microbiological surveillance for invasive pneumococcal disease (IPD) among admissions of all ages at Kilifi County Hospital was linked to the Kilifi Health and Demographic Surveillance System from 1999-2016. We calculated the incidence rate ratio (IRR) comparing the pre-vaccine and post-vaccine eras, adjusted for confounding, and reported percent reduction in IPD as 1-IRR. Annual cross-sectional surveys of nasopharyngeal carriage were conducted from 2009-2016.\n\nFindingsSurveillance identified 667 IPD cases in 3,211,403 person-years of observation. IPD incidence in children <5 years fell sharply in 2011 following PCV10 introduction, and remained low (PCV10-type IPD: 60{middle dot}8 vs 3{middle dot}2/100,000 [92% reduction; 95%CI: 78, 97]; overall IPD: 81{middle dot}6 vs 15{middle dot}3/100,000 [68% reduction; 95%CI: 40, 83]; 1999-2010 vs 2012-2016). PCV10-type IPD also declined significantly in unvaccinated age groups (<2 months, 5-14 years, [≥]15 years), with estimated reductions of 100%, 74%, and 81%, respectively. There was no significant change in the incidence of non-PCV10 type IPD. In children aged <5 years, PCV10-type carriage declined by 74% and non-PCV10-type carriage increased by 71%.\n\nInterpretationIntroduction of PCV10 in Kenya resulted in a substantial reduction in PCV10-type IPD in children and adults without significant replacement disease. These findings suggest that routine infant PCV10 immunization programmes with catch-up campaigns will provide substantial direct and indirect protection in low-income settings in tropical Africa.

epidemiology↗