Demographic data, medical history of chronic

conditions, date of vaccination and type of vaccine were collected using a structured questionnaire. For the assessment of influenza vaccine effectiveness, children were defined as vaccinated if they had received at least one dose more than 14 days before symptom onset. An influenza-confirmatory laboratory test was carried out in all children. The virus was detected through nasopharyngeal sample collection; stable viral transport medium was added to swabs. Specimens were collected and analysed by using a real-time reverse transcriptase-polymerase chain reaction (RT-PCR). In six centres the tests were analysed in internal laboratories, whereas Vemurafenib concentration the others sent the specimens to certified external laboratories. The first phase of the study was performed

in the 2011–2012 influenza season and was used as a pilot study to refine the 2012–2013 investigation. In order to concentrate enrolment and laboratory tests in the epidemic period the coordinator centre gave the start-up on the basis of data on influenza epidemics in Italy provided from the National surveillance of ILI incidence [9]. The inclusion of children took place between 1 February and 31 March 2012 MAPK Inhibitor Library (for the 2011–2012 season), and between 14 January and 15 March 2013 (for the 2012–2013 season). The inclusion periods were the same for all centres. Data were analysed according to a test-negative case-control study design: all children with a positive confirmatory laboratory test (to one of the viruses contained in the seasonal vaccine) were included as cases, whereas controls were children with a negative test. For effectiveness evaluation, odds of influenza vaccination were compared in cases and controls. The following paediatric hospitals and departments to were participating: Giannina Gaslini Paediatric Hospital (Genova); Regina Margherita Paediatric Hospital (Torino); Department of Paediatrics, University of Padova; Paediatric Department, Treviso Hospital (Treviso); Anna Meyer Children’s University Hospital (Firenze); Department of Paediatrics,

University of Perugia; Pharmacology and Paediatrics and Developmental Neuroscience, Università Cattolica S. Cuore (Roma); Bambino Gesù Paediatric Hospital (Roma); Santobono-Pausilipon Paediatric Hospital-Virologic Unit Cotugno (Napoli); Giovanni Di Cristina Paediatric Hospital (Palermo); University Hospital of Messina. A common study protocol was approved by the Ethics Committee of each clinical centre. The study was coordinated by the National Centre of Epidemiology of the National Institute of Health in Rome. Data were analysed with SPSS (v. 21.0). T-test was used to compare means, Wilcoxon–Mann–Whitney non-parametric test was used to compare medians and Chi-square test was used to compare percentages. Adjusted odds ratios (ORs) and 95% confidence intervals (CI) were estimated through a logistic regression model.