Risks and benefits of vaccinations.

Any medical intervention is expected to prevent sickness and complications of a disease rather than to induce them. This is true for therapy as well as prophylaxis. Special formulas have been developed to calculate the risks and benefits of vaccinations simply but with sufficient accuracy. The risk ratio (Q) tells how many times the risk of contracting certain complications or even death from a disease is greater in unvaccinated than in vaccinated individuals. The risk difference (D) directly expresses the number of complications or deaths that may be prevented by a certain vaccination. It is even possible to evaluate the epidemiologic trend of a disease and to calculate or estimate the point of time when the risks of disease and vaccination are just balanced, ie, when a vaccination has lost its beneficial effect. Vaccinations against measles, poliomyelitis and tick borne encephalitis in Austria are highly beneficial. BCG vaccination is still beneficial on a low level in Austria as far as protection against tuberculosis is concerned. This effect will persist for the rest of this century. The benefit of pertussis vaccination depends on the local epidemiologic situation. It has expired for non-risk groups in Austria since 1976 but continues to persist in the US.