Cohort Profile: The Kilifi Vaccine Monitoring Study

Adetifa, Ifedayo; Bwanaali, Tahreni; Wafula, Jackline; Mutuku, Alex; Karia, Boniface; Makumi, Anne; Mwatsuma, Pauline; Bauni, Evasius; Hammitt, Laura L.; Nokes, D. James; Maree, Ephantus; Tabu, Collins; Kamau, Tatu; Mataza, Christine; Williams, Thomas N.; Scott, J. Anthony G.

doi:10.1093/ije/dyw202

Cited by 18 publications

(18 citation statements)

References 22 publications

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“…As the vaccine service expanded, we incorporated a further 15 clinics between 2011-26. (23) As previously described, children who are residents of KHDSS, attending clinics for vaccination, are matched electronically to the KHDSS population register and all the vaccinations they received are recorded at the clinic in real time. (23,24) Data are entered using laptop computers at the vaccine clinics and are synchronised to a bespoke MySQL v5.6.19 relational database at the main facility through weekly hard-copy transfers on laptops.…”

Section: Study Setting and Populationmentioning

confidence: 99%

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

Adetifa

Karia

Mutuku

et al. 2018

Preprint

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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.We found coverage surveys in the 2 nd 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.Coverage surveys in 12-23 month old children overestimate protection by ignoring timeliness, and survivor and recall biases.

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Section: Study Setting and Populationmentioning

confidence: 99%

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

Adetifa

Karia

Mutuku

et al. 2018

Preprint

Self Cite

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“…Here we use a vaccine registry in Kenya [23] to quantify errors in routine coverage methods, to estimate the magnitude of survivor bias, contrast coverage with timeliness and use both measures to estimate population immunity. Finally, we examine the risk factors for delayed immunisation and illustrate the breadth of inequality in both coverage and timeliness across different birth cohorts and different locations.…”

Section: Introductionmentioning

confidence: 99%

Coverage and timeliness of vaccination and the validity of routine estimates: Insights from a vaccine registry in Kenya

Adetifa

Karia

Mutuku

et al. 2018

Vaccine

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HighlightsA high coverage is essential if the full benefits of vaccines are to be enjoyed.A vaccine registry can help quantify the errors in coverage estimates from surveys.Vaccination coverage obtained using a survey approach overestimates coverage by 2%.Survey and administrative methods underestimate fully immunised children by ≥10%.Non-hospital delivery and stock-outs were associated with failure to vaccinate.

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“…All vaccines were captured by the Kilifi Vaccine Monitoring System, a registry in which data clerks at 26 clinics serving the KHDSS link vaccination at the point of delivery to the child's identification in the KHDSS. 9 Coverage with PCV10 increased sharply during the catch-up campaign and slowly thereafter ( Figure 1, Supplemental Table 1). Coverage with ≥2 PCV10 doses in 2-11 month olds was 80% in 2011 and 84% in 2016; coverage with ≥1 dose in 12-59 month olds was 66% and 87%, respectively.…”

Section: Vaccine Introduction and Monitoringmentioning

confidence: 99%

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

Hammitt

Etyang

Morpeth

et al. 2018

Preprint

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Background: 10-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. Methods: Clinical 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 postvaccine eras, adjusted for confounding, and reported percent reduction in IPD as 1-IRR. Annual crosssectional surveys of nasopharyngeal carriage were conducted from 2009-2016.Findings: Surveillance 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: 60·8 vs 3·2/100,000 [92% reduction; 95%CI: 78, 97]; overall IPD: 81·6 vs 15·3/100,000 [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%.

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Cohort Profile: The Kilifi Vaccine Monitoring Study

Cited by 18 publications

References 22 publications

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

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

Coverage and timeliness of vaccination and the validity of routine estimates: Insights from a vaccine registry in Kenya

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

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