The history of vaccination

A very early form of vaccination known asvariolation was developed several thousand years agoin China. It involved the application of materials fromsmallpox sufferers in order to immunize others. In1796 Edward Jenner developed a safe method, usingcowpox to successfully immunize a young boy against smallpox, and this practice was widely adopted. Vaccinations against other viral diseases followed, including the successful rabies vaccination by Louis Pasteur in 1886. The nature of viruses however was not clear to these researchers.

In 1892, Dmitry Ivanovski showed that a disease of tobacco plants, tobacco mosaic disease, could be transmitted by extracts that were passed through filters fine enough to exclude even the smallest known bacteria.

In 1903, it was suggested for the first time that transduction by viruses might cause cancer. Francis Peyton Rous described such an oncovirus in chickens in 1911; it was later called Rous sarcoma virus1 and understood to be a retrovirus. Several other cancer-causing retroviruses have since been described.

While plant viruses and bacteriophages can be grown comparatively easily, animal viruses normally require a living host animal, which complicates their study immensely. In 1931, it was shown that influenza virus could be grown in fertilized chicken eggs, a method that is still used today to produce vaccines. In 1937, Max Theiler managed to grow the yellow fever virus in chicken eggs and produced a vaccine from an attenuated virus strain; this vaccine saved millions of lives and is still being used today.

The first virus that could be crystalized and whose structure could therefore be elucidated in detail was tobacco mosaic virus (TMV), the virus that had been studied earlier by Ivanovski and Beijerink.

In 1935, Wendell Stanley achieved its crystallization for electron microscopy and showed that it remains active even after crystallization. Bernal and Fankuchen obtained clear X-ray diffraction pictures of the crystallized virus in 1941.

In 1975, the functioning of oncoviruses was clarified considerably. Until that time, it was thought that these viruses carried certain genes called oncogenes which, when inserted into the host's genome, would cause cancer. A worldwide vaccination campaign led by the UN World Health Organization resulted in the eradication of smallpox in 1979.