This register based observational study aims to extend the existing knowledge on non-specific effects of non-live vaccines by testing the above finding, that delayed vaccination with Diphtheria, Tetanus, acellular Pertussis - Inactivated Polio vaccine - Haemophilus influenzae type b (DTaP-IPV-Hib) is associated with lower risk of developing atopic dermatitis before 1 year of age in the Danish birth cohorts from 1997-2012.