A universal influenza vaccine is one of the largest unmet medical needs.
Influenza virus burden on public health.
Yearly 250,000 to 500,000 people die from seasonal influenza, and on average 3 to 5 million hospitalizations occur each year. Immunocompromised individuals, infants and the elderly constitute the main risk groups, with 90% of deaths occurring in the latter group.
There is a permanent threat of a new pandemic caused by novel influenza viruses that may emerge from birds or pigs. The four influenza pandemics of the last century have caused more than 50 million deaths. Avian influenza viruses of the H5N1 and H7N9 subtypes cause an ever-increasing number of human cases with high mortality rates.
Limitations of currently used influenza vaccines.
Current seasonal influenza vaccines fail to afford broad-protective and long-lasting immunity, and provide no or very little protection against avian or pandemic influenza viruses.
1) They have to be updated every season in order to antigenetically match the epidemic strains that, due to continuous antigenic drift, escape from the immunity that builds up in the human population.
2) They have suboptimal immunogenicity and efficacy in the groups at the highest risk of severe disease.
3) They mainly aim at inducing virus-specific antibody responses, thereby largely failing to provide sufficient protection against multiple subtypes of influenza A virus.
Even natural influenza virus infections fail to afford broad ‘universal’ protection since healthy individuals on average suffer from influenza A every ten to twenty years.
In order to develop a universal influenza vaccine that induces robust and long-lasting protection against infection with influenza A viruses of ideally all subtypes, we have to “do better than Nature”.