Early childhood vaccination and subsequent mortality or morbidity: are observational studies hampered by residual confounding? A Danish register-based cohort study.

The results suggested a beneficial impact of MMR on under-five mortality but did not support the hypothesis that DTP is detrimental, since the group of children with fewer DTP vaccinations experienced increased mortality. The results of the study may to some degree be prone to residual confounding since an unexpected association between MMR vaccination and hospitalisation for accidents was observed.