Patients in the Phase I and II studies responded favourably to the treatment, which could pave the way for increased usage of cell culture-derived vaccines for treating seasonal and avian influenza. The use of cell culture to produce the vaccine offers considerable advantages over traditional hens' eggs, which could better equip the world to tackle a flu pandemic should it arise. John Oxford, professor of Virology at Queen Mary School of Medicine, London said: "Cell culture technology could represent the future of influenza vaccine production. Baxter has demonstrated the ability to rapidly make large quantities of the vaccine that may protect people against divergent H5N1 viruses." Baxter has claimed its H5N1 vaccine could be ready within 12 weeks of an influenza outbreak, compared with 20 to 28 weeks if traditional methods are used. In addition, cell culture does not suffer from the seasonality of egg-based production, which requires embryonated eggs. The difficulty of obtaining these during an avian flu pandemic would be compounded if chicken populations were decimated during the outbreak. The research found 7.5µg and 15µg vaccine doses showed efficacy but Baxter is planning on testing it at 1.9µg in a follow up study, which if effective would increase the likelihood of having sufficient vaccine in the case of an outbreak. Although there appears to be advantages to using cell culture the trial programme does leave itself open for criticism in some areas. The primary concern is that Baxter's study used determination of functional neutralizing-antibody to measure effectiveness. This differs from the standard used by the FDA and other research papers, hemagglutination-inhibition, which raises questions over the efficacy of the vaccine. However, this has been defended by the researchers who believe their measure equates to protection and is more sensitive to detection of anti-H5 antibodies. In addition, Baxter is said to be in discussions with the FDA over the standard. Whether cell culture represents a significant breakthrough in preparations against an avian influenza outbreak remains to be seen. At present there are those that believe that an overarching strategy is needed more urgently than different approaches to the problem. Speaking to the Canadian Press, Dr John Treanor, from the University of Rochester, New York, said: "From a scientific point of view I think we are in a scenario now where there are many different ... alternative strategies that you could use and it's really not clear how much of an advantage one might have over another." Although H5N1 production in cell culture is new, facilities for manufacturing seasonal flu vaccine are in place, with Novartis and Sanofi-Aventis both involved.