In conclusion, the impact of the second H1N1 2009 winter epidemic was still substantial although significantly less than in 2009. It had a lower peak occurring approximately five weeks later than in 2009, affected similar individuals, was similar in clinical severity, carried a similar mortality rate. In patients with H1N1 2009 infection requiring ICU admission a number of apparent vaccination failures were observed. Based on these data and despite the deployment of the vaccination, a second season of H1N1 2009 influenza may still have a substantial intensive care impact.