Monitoring the introduction of pneumococcal conjugate vaccines into West Africa: design and implementation of a population-based surveillance system.

Routine use of pneumococcal conjugate vaccines (PCVs) in developing countries is expected to lead to a significant reduction in childhood deaths. However, PCVs have been associated with replacement disease with non-vaccine serotypes. We established a population-based surveillance system to document the direct and indirect impact of PCVs on the incidence of invasive pneumococcal disease (IPD) and radiological pneumonia in those aged 2 months and older in The Gambia, and to monitor changes in serotype-specific IPD. Here we describe how this surveillance system was set up and is being operated as a partnership between the Medical Research Council Unit and the Gambian Government. This surveillance system is expected to provide crucial information for immunisation policy and serves as a potential model for those introducing routine PCV vaccination in diverse settings

Rapid growth is a dominant predictor of hepcidin suppression and declining ferritin in Gambian infants.

Iron deficiency and iron deficiency anemia are highly prevalent in low-income countries, especially among young children. Hepcidin is the major regulator of systemic iron homeostasis. It controls dietary iron absorption, dictates whether absorbed iron is made available in circulation for erythropoiesis and other iron-demanding processes, and predicts response to oral iron supplementation. Understanding how hepcidin is itself regulated is therefore important, especially in young children. We investigated how changes in iron-related parameters, inflammation and infection status, seasonality, and growth influenced plasma hepcidin and ferritin concentrations during infancy using longitudinal data from two birth cohorts of infants in rural Gambia (n=114 and n=193). This setting is characterized by extreme seasonality, prevalent childhood anemia, undernutrition, and frequent infection. Plasma was collected from infants at birth and at regular intervals, up to 12 months of age. Hepcidin, ferritin and plasma iron concentrations declined markedly during infancy, with reciprocal increases in soluble transferrin receptor and transferrin concentrations, indicating declining iron stores and increasing tissue iron demand. In cross-sectional analyses at 5 and 12 months of age, we identified expected relationships of hepcidin with iron and inflammatory markers, but also observed significant negative associations between hepcidin and antecedent weight gain. Correspondingly, longitudinal fixed effects modeling demonstrated weight gain to be the most notable dynamic predictor of decreasing hepcidin and ferritin through infancy across both cohorts. Infants who grow rapidly in this setting are at particular risk of depletion of iron stores, but since hepcidin concentrations decrease with weight gain, they may also be the most responsive to oral iron interventions

Project management for the establishment of the Gambian pneumococcal surveillance system: major dependency relationships.

<p>Project management for the establishment of the Gambian pneumococcal surveillance system: major dependency relationships.</p

Clinical criteria for suspected pneumonia, meningitis, and septicaemia.

a<p>Raised respiratory rate for age is defined as greater than 50 breaths per minute for children at least 2 months but less than 12 months, and as greater than 40 breaths per minute for children at least 12 months but less than 60 months.</p>b<p>Impaired consciousness is defined as V, P, or U on the AVPU score, where A is if the patient is alert, V if responsive to verbal stimulus, P if responsive to pain stimulus, and U if unresponsive.</p>c<p>Prostration is defined as inability to drink or breast feed, or to remain in a seated position in a child otherwise able to do so.</p>d<p>Severe malnutrition is defined according to the WHO definition.</p

Map of catchment area for the surveillance system in The Gambia, including settlements, primary health care (PHC), and other health facilities.

<p>Map of catchment area for the surveillance system in The Gambia, including settlements, primary health care (PHC), and other health facilities.</p

Case definitions for pneumonia, meningitis, and septicaemia.

<p>Case definitions for pneumonia, meningitis, and septicaemia.</p

Performance indicators for the Gambian pneumococcal surveillance system and the methods for measuring them.

<p>Performance indicators for the Gambian pneumococcal surveillance system and the methods for measuring them.</p

Flow chart for the Gambian pneumococcal surveillance system.

<p>Flow chart for the Gambian pneumococcal surveillance system.</p