The present invention relates to vaccines comprising at least one mRNA encoding at least one antigen for use in the treatment of a disease in newborns and/or infants, preferably exhibiting an age of not more than 2 years, preferably of not more than 1 year, more preferably of not more than 9 months or even 6 months, wherein the treatment comprises vaccination of the newborn or infant and eliciting an immune response in said newborn or infant. The present invention is furthermore directed to kits and kits of parts comprising such a vaccine and/or its components and to methods applying such a vaccine or kit.