By Fergus Walsh
BBC News medical correspondent
British scientists have begun work on a vaccine against the H1N1 swine flu virus.
Inside the lab where experts are working on a swine flu vaccine
Their efforts are under way at the National Institute for Biological Standards and Control (NIBSC) in Hertfordshire.
The NIBSC is one of a small group of influenza centres around the world which will create a seed vaccine strain which could then be grown in bulk by manufacturers.