Changes of risk and benefit in immunization against pertussis and tuberculosis.

In the case of infectious diseases with decreasing morbidity and mortality, the beneficial effects of vaccination should be reevaluated regularly with the help of special formulae. This procedure can be simplified by calculation of the epidemiologic trend and the so-called borderline risk Rlim, meaning the borderline number of complications when risks of the disease and risks of vaccination are equal. This method allows to estimate when the vaccination against a certain disease will lose its beneficial effect. A follow-up of the mortality of whooping cough in Austria leads to the conclusion that vaccination against whooping cough has lost its justification. In case of BCG vaccination the borderline mortality is not yet reached in Austria, although tuberculosis mortality and the number of prevented cases have decreased already to a very low level.