Over the centuries, numerous myths have been associated with Jenner’s discovery in attempts to either deify him or criticize him. Reproduced for noncommercial research purposes from reference. (B) Old illustration depicting a horsepox lesion on the arm of 5-year-old John Baker, who was inoculated with the material taken from a horsepox lesion (equination) on the hand of a stableman by Edward Jenner. (A) Old illustration depicting a cowpox lesion on the finger of milker William Plowman 5 days after the onset of vesicle formation.
But was that disease of horses caused by the orthopoxvirus we know today as horsepox virus? Again, this was impossible to know at the time. This procedure was referred to as equination, and Jenner, as well as other British and Italian physicians, used it successfully in the following years. Actually, Jenner was convinced that the best protective results were obtained when the transmission chain horse–cow–human was followed. The horse lymph was scarified directly on a person’s arm or first inoculated in cows, and then the cow lymph was passed to a person ( Fig 1). Many other experimental inoculations were reported by Jenner in the same manuscript, and in some cases, the vaccine material was obtained from lesions of horses affected by the so-called horsepox, a disease similar to cowpox. Thus, Jenner was unaware of the true biological nature of the vaccine material, which was called indistinctly cowpox virus or vaccinia virus. Today, we know that infection with one orthopoxvirus elicits cross-immunity against subsequent infection with another orthopoxvirus in humans -something that Jenner could not have known since viruses did not begin to be identified until the end of the 19th century. Instead, it was a related virus from the same family (Poxviridae) and genus ( Orthopoxvirus). īut what actually formed the basis for protection? Different from most current vaccines, the material used for smallpox vaccination was not an attenuated or inactivated form of the virus that caused the disease: variola virus. As time passed, history continued to faithfully relay the information that the smallpox vaccine contains cowpox virus.
These and other findings were gathered in a manuscript published in 1798, and a couple of years later, the procedure was named vaccination (from Latin “vacca,” “cow”). Because the boy did not develop smallpox, Jenner was convinced of the “preventive power” of cowpox. In one experiment, Jenner scarified the arm of an 8-year-old boy with the material of a cowpox lesion obtained from the hand of a milkmaid, and 6 weeks later, he scarified the arm of the boy again with smallpox-derived material. The disease induced pustular lesions localized to the teats of dairy cattle and the hands of milkmaids, which resembled smallpox lesions.
In 1796, the British country doctor Edward Jenner decided to test the hypothesis that previous contact with a disease of cattle known as cowpox would prevent the development of smallpox. Next-Generation Sequencing (NGS) technologies applied to genomic studies of modern and old smallpox vaccines are helping to sort out these puzzles.ĭemystifying Jenner reveals an even more powerful figure But what of previous centuries-was cowpox or horsepox the virus used? Or was it actually vaccinia virus that was being used, and if so, how did this come about? After all, vaccinia virus has never been reported to cause natural infections in animals, except for escapee vaccine strains in Brazil and India. For the 20th century, we certainly know the answer: vaccinia virus. The main mystery concerns the true origin of the vaccine matter used by Jenner and subsequent early vaccinators. The intriguing history of the smallpox vaccine is replete with mythology that continues to fascinate researchers today. However, it was only in 1980 that the World Health Organization finally declared smallpox eradicated after an intense worldwide vaccination campaign. Smallpox has claimed hundreds of millions of lives over the centuries. The discovery of smallpox vaccination by Edward Jenner in 1796 gave a new perspective to science in the struggle against this devastating disease.
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