Vaccinations (at least against communicable infections) do not have effects only on the vaccinated person but also on (possibly unvaccinated) persons in his or her neighbourhood. It has been shown that a valid evaluation of the effects of a vaccine has to be based on knowledge of which protection against infection (and disease) the vaccine gives, e.g. does the vaccine give a total protection or is the protection depending the "amount of infectiousness" confronting the vaccinated person.

Lately there has started a discussion of how to measure vaccine efficacy for vaccines that does not only lower the susceptibility to infection but also the infectiousness.

In the seminar I will try to point at some of the problems that are particular to the study vaccine effects.