Vaccines have moved on considerably since the first ‘vaccine’ against smallpox, based on the work of Edward Jenner during the eighteenth century. Dr Jenner observed that milkmaids who developed cowpox (caused by a similar but weaker virus to smallpox) never contracted smallpox. These observations led him to experiment in vaccinating patients including an eight-year-old boy with cowpox virus obtained from pus-filled blisters on a young milkmaid’s hand, before later challenging them with smallpox virus.