This all makes sense except perhaps for the flu. Only about 30% of people that come down with "flu like symptoms" actually have the flu. On the other hand the

This all makes sense except perhaps for the flu. Only about 30% of people that come down with "flu like symptoms" actually have the flu. On the other hand the effective of flu vaccines can vary widely from year to year. This is because it takes months to make all the doses that are needed so the vaccine make up, which changes every year, has to be estimated in the advance. The actual prevalent flu though can change significantly by the time flu season starts. The upshot is that the public doesn't necessarily perceive the benefit of the shot because a) they might get what they think is the flu (but isn't) and b) they might get a variant of flu that was not adequately covered by the vaccine. Obviously a more universal flu vaccine would help out a lot.