[Changes in the benefit of immunization].

The beneficial effects and the risks of vaccinations may be calculated by means of special formulas (N,Q,D). Changes in the effect of vaccinations may be substantiated by constant (eventually computerized) reevaluation of the present epidemiologic situation with the help of the above mentioned formulas. Another possibility lies in the calculation of the epidemiologic trend and determination of Rlim, the latter meaning the borderline number of complications of a certain disease, when risks as consequence of the disease or of the vaccination are about equal (D = 0). The follow-up of the epidemiologic situation over many years allows the estimation when this will be the case or, in other words, when the vaccination against the disease in question is not meaningful any more and has lost its beneficial effect and practical importance. In case of smallpox the risk of importation of the disease is practically zero; this means that N and Q less than 1 and D less than 0 thus underlining the view that the compulsory vaccination of the newborn is obsolete. A follow up of the case mortality of whooping cough in Austria over the past 15 years leads to the conclusion that Rlim, when calculated according to Ehrengut (that means that deadly risks of vaccination, r, are considered to be 2,4 x 10(-5), has been reached already in 1971. When calculated according to the WHO(r = 0,1 x 10(-5)) this will be the case by the end of 1976. In case of BCG vaccination the borderline mortality (Rlim) is not yet reached in Austria. The total number of deaths from tuberculosis that have been prevented by vaccination is already very low. The beneficial effect of this vaccination is much more expressed however when the prevention of leucemic deaths, as quoted by Davignon et al. (1970, 1971) and Rosenthal et al. (1972), is taken for granted. More observations will be necessary to clarify that point.