Developing vaccines against potential pandemic influenza viruses

Abstract In the event of an influenza pandemic, there will be an urgent need for a vaccine. The human infections with influenza A (H5N1) and A (H9N2) viruses served as pandemic warnings and initiated worldwide efforts to develop suitable vaccines. This was not straightforward however, due to safety considerations and many practical problems that were encountered. This is primarily on account of the three main strategies for H5 vaccine development: attenuation of the pathogenic A/Hong Kong/97 (H5N1) virus; expression of H5 haemagglutinin in baculovirus vectors; use of avirulent H5 avian viruses. Progress with H9 vaccine development is also reviewed. Over the past 2 1 2 years, we have learnt a great deal about our ability to respond to an influenza pandemic. Some of the improvements that could be made for the future, are summarised.