Studies from low-income countries show, that vaccines may have effects on overall mortality, so-called non-specific effects, which cannot be explained by the effect on the targeted infection. We investigated if vaccines have non-specific effects on infectious disease morbidity in Denmark, and we found beneficial non-specific effects of measles-mumps-rubella vaccine, which have now been confirmed in other high-income settings. Danish investment in research in low-income countries may lead to important new insights with consequences not only for the recipient country but also for Denmark.