BMC Infectious Diseases
(Accessed 13 December 2014)
http://www.biomedcentral.com/bmcinfectdis/content

Research article
Natural attack rate of influenza in unvaccinated children and adults: a meta-regression analysis
Kavisha Jayasundara1*, Charlene Soobiah2, Edward Thommes13, Andrea C Tricco24 and Ayman Chit15
Author Affiliations
BMC Infectious Diseases 2014, 14:670 doi:10.1186/s12879-014-0670-5
Published: 11 December 2014
Abstract (provisional)
Background
The natural (i.e. unvaccinated population) attack rate of an infectious disease is an important parameter required for understanding disease transmission. As such, it is an input parameter in infectious disease mathematical models. Influenza is an infectious disease that poses a major health concern worldwide and the natural attack rate of this disease is crucial in determining the effectiveness and cost-effectiveness of public health interventions and informing surveillance program design. We estimated age-stratified, strain-specific natural attack rates of laboratory-confirmed influenza in unvaccinated individuals.
Methods
Utilizing an existing systematic review, we calculated the attack rates in the trial placebo arms using a random effects model and a meta-regression analysis (GSK study identifier: 117102).
Results
This post-hoc analysis included 34 RCTs (Randomized Control Trials) contributing to 47 influenza seasons from 1970 to 2009. Meta-regression analyses showed that age and type of influenza were important covariates. The attack rates (95% CI (Confidence Interval)) in adults for all influenza, type A and type B were 3.50% (2.30%, 4.60%), 2.32% (1.47%, 3.17%) and 0.59% (0.28%, 0.91%) respectively. For children, they were 15.20% (11.40%, 18.90%), 12.27% (8.56%, 15.97%) and 5.50% (3.49%, 7.51%) respectively.
Conclusions
This analysis demonstrated that unvaccinated children have considerably higher exposure risk than adults and influenza A can cause more disease than influenza B. Moreover, a higher ratio of influenza B:A in children than adults was observed. This study provides a new, stratified and up to-date natural attack rates that can be used in influenza infectious disease models and are consistent with previous published work in the field.

Study protocol
Multicenter case–control study protocol of pneumonia etiology in children: Global Approach to Biological Research, Infectious diseases and Epidemics in Low-income countries (GABRIEL network)
Valentina Sanchez Picot, Thomas Bénet, Melina Messaoudi, Jean-Noël Telles, Monidarin Chou, Tekchheng Eap, Jianwei Wang, Kunling Shen, Jean-William Pape, Vanessa Rouzier, Shally Awasthi, Nitin Pandey, Ashish Bavdekar, Sonali Sanghvi, Annick Robinson, Bénédicte Contamin, Jonathan Hoffmann, Maryam Sylla, Souleymane Diallo, Pagbajabyn Nymadawa, Budragchaagiin Dash-Yandag, Graciela Russomando, Wilma Basualdo, Marilda M Siqueira, Patricia Barreto, Florence Komurian-Pradel, Guy Vernet, Hubert Endtz, Philippe Vanhems, Gláucia Paranhos-Baccalà* and and on behalf of the pneumonia GABRIEL network
Author Affiliations
BMC Infectious Diseases 2014, 14:635 doi:10.1186/s12879-014-0635-8
Published: 10 December 2014
Abstract (provisional)
Background
Data on the etiologies of pneumonia among children are inadequate, especially in developing countries. The principal objective is to undertake a multicenter incident case-control study of <5-year-old children hospitalized with pneumonia in developing and emerging countries, aiming to identify the causative agents involved in pneumonia while assessing individual and microbial factors associated with the risk of severe pneumonia.
Methods/design
A multicenter case-control study, based on the GABRIEL network, is ongoing. Ten study sites are located in 9 countries over 3 continents: Brazil, Cambodia, China, Haiti, India, Madagascar, Mali, Mongolia, and Paraguay. At least 1,000 incident cases and 1,000 controls will be enrolled and matched for age and date. Cases are hospitalized children <5-years with radiologically confirmed pneumonia, and the controls are children without any features suggestive of pneumonia. Respiratory specimens are collected from all enrolled subjects to identify 19 viruses and 5 bacteria. Whole blood from pneumonia cases is being tested for 3 major bacteria. S. pneumoniae-positive specimens are serotyped. Urine samples from cases only are tested for detection of antimicrobial activity. The association between procalcitonin, C-reactive protein and pathogens is being evaluated. A discovery platform will enable pathogen identification in undiagnosed samples.
Discussion
This multicenter study will provide descriptive results for better understanding of pathogens responsible for pneumonia among children in developing countries. The identification of determinants related to microorganisms associated with pneumonia and its severity should facilitate treatment and prevention.