Highly publicised vaccine scares and recent debates about the risks suggest that public trust in immunisation programmes is fragile. For instance, the recent outbreak of Measles in Wales was the direct result of almost fifteen years of distrust for the MMR vaccine in the UK. This article shows how the latest science on risk communication will help critical actors, especially policy-makers, to build trust when they communicate risks to citizens and patients. The article offers policy advice on risk communication based on the results of three vaccines case studies. Five procedural principles which were developed for the UK government - the so-called "five As" of public risk communication are used to structure the discussion. Conclusions and recommendations suggest ways to move forward and build a two-way proactive risk communication practice.