Vaccine development for new influenza A (H1N1) and vaccine candidates for future pandemics

On the 11th of June 2009, the first influenza pandemic of the 21st century was announced by the WHO. This pandemic H1N1 influenza A virus appeared to be a result of reassortment of classical swine H1N1, human H3N2, Avian, and Eurasian swine influenza viruses over the years. Since it has not circulated in humans before, the population is immunologically naïve and the virus can easily spread globally. On the 25th of October 2009, over 440,000 confirmed cases have been reported worldwide, of which >1% was fatal. Vaccination is considered to be the best defensive strategy against an influenza outbreak. Conventional influenza vaccines contain hemagglutinin and vaccine production can only start when the consensus virulent strain is identified. During a pandemic outbreak, time is sparse and therefore dose and time sparing strategies as well as vaccines leading to cross-protection and/or heterosubtypic immunity are desirable. These options for novel influenza vaccines are discussed in this paper