Influenza virus A/H1N1 2009 is a specific combination of internal genes explaining its pandemic character. Compared with seasonal influenza, influenza like illnesses were more frequent in young healthy people (children and adults). In France, among 1 329 severe cases, 20% had no risk factors and 312 subjects (23.5%) died. Compared with young adults without RF, the risk of severe case was 10-fold in pregnant women or 5-fold in infants (< 1 yr). A risk factor (in similar age group/without risk factor) multiplied the risk by 20 to 30 between 2 and 64 yrs, by 18 after 64 yrs, by 130 in infants < 1 yr, by over 300 between 1 and 2 yrs, and by 20 in pregnant women. A/H1N1 vaccination, proposed to the French population, was organized by the State in dedicated vaccination centers, in a staggered approach relying on pre-established priority groups, the sequential arrival of vaccines, the type of available vaccines, most often in multidoses. The official recommendations were adapted over time (age group, number of doses, type of vaccine utilized). Pandemrix and Focetria were the most casual; from mid-November 2009, Panenza was available. There was a 3 weeks interval between seasonal vaccination and pandemic one. Global coverage rate achieved is 8%. No peculiar severe adverse events and no signal of Guillain Barré syndrome were notified to the national pharmacovigilance net.