Prior to Jenner, variolation, (Fenner et al., 1988) inoculation of variola into the skin or nasal mucosa, was used to reduce the risk of smallpox. Jenner himself was variolated as a child. Skin inoculation with a small amount of fresh pustule fluid, likely to have contained large numbers of infectious virions, produced a local lesion with satellite pustules, but generalized rash was reported to be less severe and mortality rates were usually 10-fold lower than with naturally acquired disease (Fenner et al., 1988) . In China, variolation was frequently performed by inoculation of the nasal mucosa. Some accounts describe blowing carefully aged scabs compounded with plant material into the nose (MacGowan, 1884). Other reports suggests that nasal insufflation was considered relatively ineffective and that nasal insertion of cotton pledgets impregnated with powdered scabs or smeared with vesicle contents was preferred (Wong and WU, 1936; Miller, 1957) . Descriptions of the latter method do not include ageing infectious material before use.