The clinical characteristics, risk factors, and outcomes of patients admitted to ICUs with H1N1 2009 were broadly similar in 2010 to those admitted in 2009 ( Table 2 ). Comparing 2010 with 2009 there were no significant differences in the distribution of cases among different age groups. In both study periods the highest number of ICU admissions occurred among patients aged between 25 and 49. There was no difference in the proportion of patients with a body mass index greater than 35 kg/m 2 , who were pregnant or post-partum or who had no known predisposing factor between that observed in 2009 and 2010 ( Table 2) . The proportion of patients with asthma or chronic obstructive pulmonary disease, chronic heart failure, or an Acute Physiology Age Chronic Health Evaluation (APACHE) III or paediatric co-existing illness was lower in 2010, but these factors were still over-represented in comparison to the general population, as they were in 2009 [3] (Table 2) admissions due to confirmed influenza in both countries [3] . The second wave occurred later in the year but resulted in similar illness severity, affected similar groups at risk and caused similar in-hospital mortality. The incidence of H1N1 2009 influenza critical illness during 2010 was higher in NZ than in Australia, which was a reversal of the pattern in 2009. However, the combined incidence over both winters was similar in both countries. We observed vaccination failure in a substantial proportion of patients for whom vaccination status was known. Our observations do not support the view that the H1N1 2009 pandemic has come to an end [13] .