Use of population based background rates of disease to assess vaccine safety in childhood and mass immunisation in Denmark: nationwide population based cohort study

Rasmussen TA, Jorgensen MR, Bjerrum S, Jensen-Fangel S, Stovring H, Ostergaard L, Sogaard OS. Use of population based background rates of disease to assess vaccine safety in childhood and mass immunisation in Denmark: nationwide population based cohort study. BMJ. 2012; 345: e5823.