Evolution happens due to genetic changes between generations of organisms. It does not take long for viruses to reproduce and make a new generation so they can evolve quickly. Some viruses carry their genetic material as DNA molecules while others, including flu viruses, have genes that are RNA based. Replication of RNA based genetic material lacks the error correction processes that are present in DNA replication mechanisms. This leads to a higher number of changes in each generation of flu virus, speeding up its evolution.

Vaccines for various disease, including flu, save millions of lives and alleviate human suffering. Yet, acceptance of vaccines is estimated at only 70% globally and as low as 40% in some countries. Attitudes towards science, government authority, personal choice and communal action influence how populations feel about vaccines, while certain players disseminate dubious information to influence opinion. Public policy initiatives and authentic, persuasive communications must complement the massive scientific effort in order to fully realise the benefits of medical science developments such as vaccines.