"Since it was set up in 1948, the World Health Organization (WHO) has used posters to influence national health policies. A recently published book celebrates the story of public health posters and their cross-cultural power. They chart decades of changing health priorities, advertising trends and government regulations, inviting the reader to reflect on how public health campaigns have evolved, and how they could be improved."
The book, Public health campaigns : getting the message across, is now in the Public Health Library (Call number RA427.8 .P83 2009, and is also available online: each chapter is a (large) PDF file.