More vaccines of different types are reaching ever more people

Two hundred years after the pioneering clinical experiments of Edward Jenner, who inoculated humans with cowpox to prevent smallpox, we find ourselves at the threshold of a golden age of vaccinology. Much attention has recently been directed at the advances in modern biotechnology that are giving rise to exciting new vaccine candidates. Nevertheless, a long and arduous journey lies between being an innovative concept and becoming a licensed product that can serve as a public health tool. In fact, few concepts survive to become products. Less well appreciated are the advances in clinical vaccine testing that allow a vaccine to progress towards licensing; the epidemiological techniques devised to appraise its effectiveness after licensing, when the vaccine is used under real life conditions; and the tactics used to achieve high levels of vaccine coverage, particularly in less developed countries.

Biotechnology has opened entire new approaches to vaccine development, such as the rational and precise attenuation of bacteria and viruses to serve as live vaccines,1 the direct inoculation with plasmid DNA encoding protective antigens (“naked DNA” vaccines), and the microencapsulation of antigens to enhance immunogenicity and modulate the kinetics and type of immune response.2 Consequently, at various stages …