We thank Matthews and Dore for agreeing with our suggestion to treat human immunodeficiency virus (HIV)-infected patients with acute hepatitis C by using combination therapy,1 although they advocate a 24-week duration because 85% of their patients with early virological response (EVR) but not rapid virological response (RVR) achieved sustained virological response (SVR) after a 24-week course in the recent ATAHC study.2 This is a key point, because the optimal duration would be the best compromise between reducing expense and toxicity on the one hand, and maximal efficacy on the other hand, given the faster and more severe evolution of HCV infection in HIV-infected patients. We agree that excluding patients who failed in the HEPAIG study to achieve RVR or EVR (n = 4) would enhance the SVR rate of 24-week course therapy. Indeed, the SVR rate in patients experiencing EVR, when assessed, was 88% (8/9), which is higher than that observed in ATAHC (74%)2 and close to the 92% obtained with a longer course in HEPAIG.1 However, the RVR rate in HEPAIG was high, particularly for the 14 patients treated for 24 ± 4 weeks (57%), compared with that observed in ATAHC (34%), whereas the EVR rate was lower (75% versus 91%). Because HCV therapy and doses were similar in these studies, this may be linked to differences in HCV genotype distribution (with a potential cluster effect), in the clinical presentation of acute hepatitis C, or in the characteristics of the patients (e.g., the HCV transmission route and perhaps the distribution in IL28B gene polymorphisms). Whatever the reasons, most patients with EVR in HEPAIG had RVR previously. Only two patients in HEPAIG experienced EVR but not RVR. Although both of these patients achieved SVR, this finding is not sufficient to draw conclusions, in contrast with the ATAHC study, where 17/20 patients with EVR but not RVR experienced SVR.2 Whether the three patients who did not experience SVR would have benefited from a longer course cannot be established from the ATAHC study. Recent cohort studies on acute hepatitis C in HIV-infected patients are quite supportive and complementary in helping to define the best strategy in treating acute hepatitis C in HIV-infected patients. They highlight the pivotal role of HCV kinetics assessment on the management of HCV therapy. From both the HEPAIG1 and ATAHC reports,2, 3 patients with RVR have to be treated for 24 weeks. For patients experiencing EVR but not RVR, SVR rate following a 24-week course ranges from 75% in the European Cohort Study4 (albeit including some patients with a 48-week course therapy) to 85% in ATAHC,2 compared with a hepatitis C virus (HCV) eradication rate of 100% (10/10) with a longer course in HEPAIG.1 Whether this mean difference of roughly 15%-20% is significant, relevant, or marginal may be debated and should only be addressed in randomized, controlled trials. Nevertheless, our conclusions parallel the recent recommendations of the NEAT consensus conference stating that it would be reasonable to aim for a 24-week course, with a longer duration reserved for those without RVR but with EVR.5 Finally, we also agree that new HCV therapies will probably lead to modifications in these propositions, not only by improving the success rate of retreatment of patients failing to respond to first line pegylated interferon–ribavirin therapy, but also as a first-line treatment of acute hepatitis C. Lionel Piroth*, Christine Larsen , Elisabeth Delarocque-Astagneau , Stanislas Pol§, * Infectious Diseases Department, University Hospital, and Université de Bourgogne, Dijon, France, Institut de Veille Sanitaire, Saint Maurice, France, Unité d'épidémiologie des maladies émergentes, Institut Pasteur, Paris, France, § Université Paris Descartes, Institut Cochin Inserm U1016 and service d'Hépatologie, APHP-Hôpital Cochin, Paris, France.