I have trained in public health and in paediatrics. I became interested in issues related to herd immunity when I got involved in the study of child health needs and vaccination coverage in Greece, back in the late 1980s; I realised that (among others) limited public health tradition in my country led to inappropriate immunisation policies. In the 1990s, I was involved in the study of various aspects of immunisation policies in Greece, including the first national survey of vaccination coverage and the study of an unprecedented epidemic of congenital rubella. It was made clear that this epidemic, which took place nearly 20 years after the introduction of vaccination for rubella in young children, was the largest ever recorded in Greece, and that the phenomenon of herd immunity played an important role in its occurrence.