Early results from a trial testing a 2009 H1N1 influenza vaccine in children look promising. Preliminary analysis of blood samples from a small group of trial participants shows that a single 15-microgram dose of a non-adjuvanted 2009 H1N1 influenza vaccine — the same dose that is in the seasonal flu vaccine — generates an immune response that is expected to be protective against 2009 H1N1 influenza virus in the majority of 10- to 17-year-olds eight to 10 days following vaccination.