Many vaccines do more than just protect individual vaccinated people. They also protect the whole community through what is known as "herd immunity" by cutting the number of sick people carrying the infection. However, this situation doesn't apply with standard flu vaccines because the virus mutates quickly, so vaccinations need to be effectively created anew each year. Vaccination campaigns have to target vulnerable people, rather than trying to vaccinate the whole population.
A number of groups are developing so-called "universal" flu vaccines, which rely on targeting conserved parts of the virus--parts that change very little. Researchers at Princeton University are looking at these universal vaccines, and believe that they can be used across the whole population. Because of this, they may actually slow down the mutation rate of the flu virus, and may also be able to create herd immunity, reducing the levels of infection across unvaccinated as well as vaccinated people.
Herd immunity only works if vaccinations are widespread, though. To create this level of protection, vaccinations need to be at levels of 83% to 94%, depending on the infection. For many diseases, the levels have dropped below this, and outbreaks of preventable viral infections are out there, putting elderly people, pregnant women and other groups at risk. While there will always be some risks from vaccination, there are also some quite major risks from what may seem to be trivial diseases. Flu isn't trivial for vulnerable people. So, bring on the universal vaccines. -- Suzanne Elvidge (email)