Finally, as the WHO Strategic Advisory Group of Experts (SAGE) recently made its recommendations for priorities in vaccination for the H1N1 pandemic in terms of the social groups (e.g., healthcare workers those with chronic medical conditions), health groups (pregnant women), and age groups [34] , the model also can be used to divide population into social/health groups. For example, to study vaccine policy for the elderly, we could divide the elderly into those living in households and those living in old age homes, since they mix differently in these two distinct settings. The model is also useful for simulations of the cost-effectiveness of vaccine and other intervention measures, such as prophylaxis treatment, perhaps in future work.  Extracorporeal life support for management of refractory cardiac or respiratory failure: initial experience in a tertiary centre INTRODUCTION: Extracorporeal Life Support (ECLS) and extracorporeal membrane oxygenation (ECMO) have been indicated as treatment for acute respiratory and/or cardiac failure. Here we describe our first year experience of in-hospital ECLS activity, the operative algorithm and the protocol for centralization of adult patients from district hospitals. METHODS: At a tertiary referral trauma center (Careggi Teaching Hospital, Florence, Italy), an ECLS program was developed from 2008 by the Emergency Department and Heart and Vessel Department ICUs. The ECLS team consists of an intensivist, a cardiac surgeon, a cardiologist and a perfusionist, all trained in ECLS technique. ECMO support was applied in case of severe acute respiratory distress syndrome (ARDS) not responsive to conventional treatments. The use of veno-arterial (V-A) ECLS for cardiac support was reserved for cases of cardiac shock refractory to standard treatment and cardiac arrests not responding to conventional resuscitation. RESULTS: A total of 21 patients were treated with ECLS during the first year of activity. Among them, 13 received ECMO for ARDS (5 H1N1-virus related), with a 62% survival. In one case of post-traumatic ARDS, V-A ECLS support permitted multiple organ donation after cerebral death was confirmed. Patients treated with V-A ECLS due to cardiogenic shock (N = 4) had a survival rate of 50%. No patients on V-A ECLS support after cardiac arrest survived (N = 4). CONCLUSIONS: In our centre, an ECLS Service was instituted over a relatively limited period of time. A strict collaboration between different specialists can be regarded as a key feature to efficiently implement the process. Extracorporeal circulation support techniques have been proposed either for treatment of cardiac and/or pulmonary failure refractory to conventional treatments in adult patients. The first device, which assured blood extracorporeal oxygenation and perfusion of isolated organs, was developed by von Frey and Gruber in 1885 [1] . The first heart-lung machine was projected by Gibbon in 1937 in order to allow open-heart surgical operations [2] . Over the years, extracorporeal circulation circuit has been improved and the technique optimized, and it is now available for clinical practice. From a general point of view, two methods of support are outlined: venovenous extracorporeal oxygenation, commonly known as ECMO, Extracorporeal Membrane Oxygenation, for respiratory function substitution and extracorporeal life support technique (ECLS) with a veno-arterial circulation for both oxygenation and hemodynamic assistance. The major indications for ECMO, in adult patients, are severe acute respiratory distress syndrome (ARDS) refractory to conventional treatments [3, 4] , and, in selected cases, post-traumatic respiratory failure, severe asthma [5, 6] , and chronic lung disease waiting for lung transplantation [7, 8] . The indications for ECLS and cardiac support are cardiac failure due to any cause, and cardiac arrest not responsive to Advanced Life Support manoeuvres. In the first case, the in-hospital mortality rate is still high (between 33% and 38%) and ECLS represents a rescue-therapy useful for refractory patients [9] . In case of in-hospital cardiac arrest, when ECLS was used after ten minutes of unsuccessful cardiopulmonary resuscitation, an increase in survival rate at ICU discharge, at 30-day and at 1-year survival was reported [10] . At a tertiary referral trauma center (Careggi Teaching Hospital, Florence, Italy) an ECLS program was developed beginning April 2008 by the Intensive Care Unit of Emergency Department in association with the Intensive Cardiac Coronary Unit of Heart and Vessel Department.