Efforts by health authorities to stress the importance of herd immunity in the light of a resurgence of seemingly vanquished childhood diseases have frequently met with poor response rates. Investigating whether reunified Berlin can achieve a desirable herd immunity of 80% ‐ 85% against diphtheria, this paper examines the potential influence of socio‐demographic variables (age, gender, social circumstances, migration background) on vaccine‐uptake. Secondly, it investigates historically diverging vaccinal policies in Berlin as well as recent changes to monitoring coverage in their effect on immunisation‐related behaviour.