Influenza is a vaccine preventable disease and influenza vaccines have been available for use in Europe since the 1960s.
A number of variants of the influenza viruses
co-circulate each year. Individuals can develop immunity to the different subtypes of influenza viruses, but there is little cross-immunity between subtypes. This is why several influenza strains must be included into combination vaccines.
Currently all influenza vaccines contain
three different influenza subtypes (trivalent): two influenza A subtypes (H1N1, H3N2),
and one influenza B subtype (Victoria or Yamagata lineage).