The World Health Organisation recognises HIV/AIDS as the number one infectious disease in the world. Doctors and scientists know that the best way to stop this disease would be to develop a vaccine to stop the 14,000 new infections with AIDS virus that occur each day worldwide. The difficulty is that scientists do not know whether an AIDS vaccine needs to stimulate the production of antibodies, molecules in the blood that recognise the virus and stop it from infecting new cells, or killer T cells that eliminate virus infected cells before the infection can spread further. Alternatively the vaccine may need to do something different to be fully effective. The team at NIBSC are studying an animal model of HIV and have found that animals vaccinated with a disabled form of the virus first are resistant to disease causing strains. This group think that events that occur within 3 weeks of vaccination are critical for the vaccine and that many of these occur in and around the gut. As a result, they will focus on unravelling these early events to enable a better AIDS vaccine to be designed and developed in the future.