Seasonal influenza constitutes a significant healthcare problem, with an estimated 17 to 50 million persons affected annually in the U.S. alone. Elderly patients are at particular risk accounting for 80-90% of influenza related deaths and morbidity. Moreover, the population > 65 years is increasing – projected from 36.6 million in 2005 to reach 71.5 million by 2030. Influenza vaccination has efficacy rates from 70-90% in young adults but on average only 40% (range 27-75%) in elderly subjects. In 2008-2009, the U.S. market for seasonal influenza vaccines was ~$11 billion.
Pandemic influenza arising from newly emerging strains of influenza virus as evidenced by the recent outbreak of the 2009 strain of influenza A H1N1 underscores the public health importance for timely and adequate supply of more immunogenic and efficacious influenza vaccines. It also illustrates how difficult it is to predict with certainty the next pandemic strain – the more virulent and less immunogenic H5N1 strain had been widely predicted to be the next pandemic strain, whereas H1N1 was what actually emerged. It is estimated that the H1N1 transient pandemic boosted the seasonal flu vaccine market by $1-$2 billion.