Correspondence (reply): In Reply

Our evaluation of the data from the German health interview and examination survey for children and adolescents (KiGGS) with regard to possible associations between vaccinations and specific health problems in children and adolescents (1) was meant as a contribution to bringing the discussion back to facts and provide answers about the situation in Germany. We did not claim to provide conclusive answers to each and every unanswered question regarding the subject of vaccination. This can be done only by means of a general overview of all available epidemiological and experimental evidence and not on the basis of individual studies.

The atopic disorders we included were diagnosed by doctors. In order to avoid biases, we did not include patients who had not been vaccinated for health reasons in our analyses.

We intentionally differentiated between individuals who had not received any vaccinations at all and those who had received at least one vaccination, because it is exactly this distinction that is of central importance in numerous inquiries to the Robert Koch-Institute. Owing to the low prevalence of unvaccinated people, however, we determined only 94 definitely unvaccinated patients out of a total of 17 641 individuals. The evaluation results did not reach statistical significance in the occurrence of atopic disorders or the frequency of infections between unvaccinated and vaccinated patients. The question of whether larger case numbers would have yielded the same differences between groups, but to a statistically significant degree, cannot be answered on the basis of our data. Such speculations would, however, also become necessary regarding those between-group differences whereby unvaccinated children tendentially have more instances of impaired health than vaccinated children. Further differentiating analyses of the KiGGS data—for example, considering the number of vaccination doses—are currently under way.

With regard to possible health effects of vaccinations, numerous studies have been published whose results partly point at associations in the direction of increased risks, partly at associations pointing in the direction of reduced risk, or no association at all. A meta-analysis by Balicer et al. showed neither a risk increasing effect nor a risk reducing effect with regard to asthma for the diphtheria/tetanus/pertussis (DTP) or Bacille Calmette-Guérin (BCG) vaccines (2). In a study including children who had received the MMR vaccine and children who had not, Bernsen et al. found an increased risk for atopic disorders after contracting measles and a reduced risk for atopic disorders after contracting rubella (3). The evaluation of the EPAAC study showed no association between vaccinations in the first year of life and the development or severity of atopic dermatitis or sensitization, even in children with an increased risk for allergies (4). The clinical guideline on preventing allergies includes a clear recommendation in favor of the vaccinations recommended by the German Federal Standing Committee on Vaccination (Ständige Impfkommission, STIKO), since systematic evaluation of the relevant literature did not yield any proof of an increased risk for allergies (although it did provide indications of a reduced risk) after vaccinations.

Whether, and the extent to which, the timing of the vaccination is important for the immune system is an important question in our opinion, but finding an answer requires specialized studies. We do not think that enough proof exists to support the conclusion that childhood diseases might prevent tumors in adulthood.