Searching for the origin of the smallpox vaccine: Edward Jenner and his little-known horsepox hypothesis

Introduction of the smallpox vaccine in Napoleonic France, as recorded in contemporary medals

The smallpox vaccine developed by Jenner in 1798 was successfully introduced in France in 1800 with the support of Napoleon Bonaparte. The medals and tokens (coin-like medals) issued to encourage early-day vaccination activities are described in the context of the changing political situation in that country. In 1800 a private society of subscribers, led by the Duke of La Rochefoucauld-Liancourt was created, along with a Vaccine Committee charged with evaluating the safety and efficacy of vaccination before deciding if vaccination should be extended to the entire population. The Vaccine Committee published a positive report in 1803, and in 1804, the Ministry of the Interior established the "Society for the extinction of smallpox in France by means of the propagation of the vaccine". The creation of the Society made smallpox vaccination an official activity of the empire, facilitating collaboration between government agencies. The vaccine institution, established by Napoleon in 1804, continued its functions until 1820 when the Royal Academy of Medicine was created and took over those functions. This case exemplifies the collaboration that was needed between science and politics to rapidly bring the recently developed smallpox vaccine to the needed population.

Live attenuated smallpox vaccine candidate (KVAC103) efficiently induces protective immune responses in mice

Smallpox, caused by the variola virus belonging to the genus Orthopoxvirus, is an acute contagious disease that killed 300 million people in the 20th century. Since it was declared to be eradicated and the national immunization program against it was stopped, the variola virus has become a prospective bio-weapon. It is necessary to develop a safe vaccine that protects people from terrorism using this biological weapon and that can be administered to immunocompromised people. Our previous study reported on the development of an attenuated smallpox vaccine (KVAC103). This study evaluated cellular and humoral immune responses to various doses, frequencies, and routes of administration of the KVAC103 strain, compared to CJ-50300 vaccine, and its protective ability against the wild-type vaccinia virus Western Reserve (VACV-WR) strain was evaluated. The binding and neutralizing-antibody titers increased in a concentration-dependent manner in the second inoculation, which increased the neutralizing-antibody titer compared to those after the single injection. In contrast, the T-cell immune response (interferon-gamma positive cells) increased after the second inoculation compared to that of CJ-50300 after the first inoculation. Neutralizing-antibody titers and antigen-specific IgG levels were comparable in all groups administered KVAC103 intramuscularly, subcutaneously, and intradermally. In a protective immunity test using the VACV-WR strain, all mice vaccinated with CJ-50300 or KVAC103 showed 100% survival. KVAC103 could be a potent smallpox vaccine that efficiently induces humoral and cellular immune responses to protect mice against the VACV-WR strain.