Variolation shortly after variolation began to outweigh the benefits of the procedure. From the 1760s, a number of individuals, including John Fewster, Peter Plett, Benjamin Jesty, and particularly Edward Jenner, were interested in the use of material from cowpox, an animal infection, to protect against smallpox. In 1796, Jenner vaccinated James Phipps, did more vaccinations in 1798, and was the first to publish evidence that cowpox protected against smallpox, was safer than variolation, and that his vaccine could be maintained by arm-to-arm transfer. The use of variolation soon began to decline as the smallpox vaccine became widely used and its benefits
History of HIV/AIDS the necessity to supply workers and because firearms became more widely available. The colonial authorities also gave many vaccinations against smallpox, and injections, of which many would be made without sterilising the equipment between uses (unsafe or unsterile injections). Chitnis "et al." proposed that both these parenteral risks and the prostitution associated with forced labor camps could have caused serial transmission (or serial passage) of SIV between humans (see discussion of this in the next section). In addition, they proposed that the conditions of extreme stress associated with forced labor could depress the immune system of workers, therefore prolonging the