By Ransdell Pierson NEW YORK, March 29 (Reuters) - MedImmune Inc. <MEDI.O> on Thursday said it had licensed Sanofi-Aventis <SASY.PA> its technology for creating viruses from segments of DNA, for use in developing vaccines against seasonal and pandemic influenza. MedImmune said it had licensed its so-called reverse genetics technology to the vaccines unit of Paris-based Sanofi-Aventis to help it construct new vaccine strains that can be used to produce human vaccines against influenza. Sanofi-Aventis has developed a potential bird flu vaccine for humans, which a panel of U.S. experts recommended in February as an interim measure until better versions are developed. It would be used after a pandemic is declared. The Sanofi vaccine would be the only U.S.-approved vaccine for the H5N1 influenza virus in case of a pandemic, if the U.S. Food and Drug Administration later approves it. "For potential pandemic influenza vaccines, reverse genetics can be a useful technology because the process does not require manufacturers to work directly with potentially highly infectious pandemic strains, such as H5N1, rather only segments of the virus's genome," MedImmune said in a release. A rising number of outbreaks of the virus in birds and humans in other countries have created concerns it could mutate into a form that is transmitted easily from human to human, and thereby cause a deadly global epidemic. Although Sanofi is the first drugmaker to seek U.S. approval for a bird flu vaccine, Novartis AG <NOVN.VX> and GlaxoSmithKline <GSK.L> are also developing H5N1 vaccines. MedImmune said it will receive an upfront payment from Sanofi-Aventis and could receive royalties on certain vaccine stockpiles or sales of other influenza products developed using its reverse genetics technology. The company, which is based in Gaithersburg, Maryland, said it is using the reverse genetics technology for its own pandemic research.