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BackgroundThe 10-valent pneumococcal conjugate vaccine (PCV10) was introduced in Nigeria without any baseline data on serotype distribution in invasive pneumococcal disease (IPD). To estimate the proportion of IPD attributable to different serotypes, in children aged MethodsWe used the carriage data from one urban and one rural setting in Nigeria, collected within five months of PCV10 introduction (2016). For Model A, we used serotype-specific adult case-fatality ratios from Denmark as proxy for IC. In the second model, we used the ratio of IPD proportions to carriage prevalence (case-carrier ratios) from Kenya (Model B) and the ratio of IPD incidence to carriage acquisition (attack rates) from the UK (Model C) as measures of serotype IC.ResultsThe models predict that serotypes with high carriage prevalence (6A, 6B, 19F and 23F) will dominate IPD. Additionally, Models B and C predictions emphasize serotypes 1, 4, 5, and 14, which were not prevalent in carriage but had high IC estimates. Non-PCV10 serotypes,6A and 19A, also dominated IPD predictions across models and settings. The predicted proportion of IPD attributed to PCV10 serotypes varied between 56% and 74% by model and setting.ConclusionCarriage data can provide preliminary insights into IPD serotypes in settings that lack robust IPD data. The predicted PCV10-serotype coverage for IPD was moderately high. However, predictions for non-PCV10 serotypes indicate that higher-valency PCVs that cover serotypes 6A and 19A may have a larger impact on IPD reductions.

BackgroundPneumococcal Conjugate Vaccines (PCVs) reduce the burden of pneumococcal disease by reducing nasopharyngeal acquisition and transmission of serotypes in the vaccines (vaccine-serotypes). Following introduction of the 10-valent PCV (PCV10) in Nigeria, we assessed the population-level impact of PCV introduction on pneumococcal carriage.MethodsWe conducted annual cross-sectional carriage and vaccination coverage surveys between 2016 and 2020 in rural and urban sites in Nigeria. We recruited a random sample of residents and used WHO-recommended laboratory methods to identify pneumococcal serotypes. We modelled prevalence ratios for the change in annual carriage prevalence using log-binomial regression, and explored the association between vaccination coverage in children FindingsWe enrolled 4,684 and 3,653 participants for the carriage surveys and 2,135 and 1,106 children for the coverage surveys in the rural and urban sites, respectively. Carriage prevalence of vaccine-serotypes declined steadily with increasing levels of PCV10 coverage among children aged ConclusionsWe found significant reduction in vaccine-serotype carriage at a population level following a steady increase in PCV10 coverage, indicating direct and indirect vaccine effects.

Adverse Events Following Immunisation (AEFI) contribute to child morbidity and mortality as they often lead to low uptake of vaccines with consequent persistence of vaccine-preventable diseases. It is essential to assess the prevalence of AEFIs in northern Nigeria, where misconceptions about immunisation exist. This study assessed the prevalence and pattern of AEFI among children less than 24 months after attending immunisation clinics in Kano, Nigeria. Using a mixed-methods design, adapted intervieweradministered questionnaires were assigned to a cross-section of 384 mother-baby pairs who presented to the immunisation clinics of selected primary healthcare centres (PHCs) within metropolitan Kano. This was followed by six sessions of focus group discussion with a sub-sample of the mothers. Logistic regression and the framework approach were used to analyse the data. The prevalence of AEFI was (43.5%, n=164), and most cases (72.4%, n=273) were mild. Fever was the most common type of AEFI reported (66.5%, n=109) and was higher among infants less than three months (44.5%, n=73). Age of the index child was the only significant predictor of AEFI (OR:0.18, 95% CI: 0.10-0.35). Our study shows that AEFI was common among children less than 24 months old in Kano. We recommend sensitisation and health education of caregivers using valuable communication strategies and sufficient training of immunisation service providers on professional ways to deliver these vaccines safely.