Immunology

The origins of inoculation against smallpox in China are mysterious. We know that the technique originated in the southern province of Sichuan, where there is a famous mountain called Emeishan which is known for its connections with both Buddhism and Taoism. The Taoist alchemists who lived as hermits in the caves of that mountain possessed the secret of smallpox inoculation in the tenth century AD.

The technique first came to public attention when the eldest son of the Prime Minister Wang Dan (957-1017) died of smallpox. Wang desperately wished to prevent this happening to other members of his family, so he summoned physicians, wise men and magicians from all over the Empire to find some remedy. One Taoist hermit came from Emeishan. This monk or nun brought the technique of inoculation and introduced it to the capital.

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Inoculation has certain dangers which set it apart from the later technique of vaccination. When one is inoculated, one has the live virus inserted into one's body. When the process is successful, one is immune for life. But the process can simply be one of direct exposure to the disease, so that one ends up with smallpox. With vaccination, the immunity conferred is only temporary, so that vaccinations have to be given every few years as "boosters". This is because vaccination uses dead viruses or some other kind of denatured virus (perhaps a related one) which cannot actually give one the disease.

At first sight it looks as if inoculation against smallpox must have been madness. Were not people just being given smallpox every time? The answer is no. And here we find the subtlety of the Chinese inoculators to be truly astounding. They practised a variety of methods for the attenuation of the deadly virus, so that the chances of getting the disease were minimized. First of all, there was a strong prohibition against taking the smallpox material from people who actually had the disease. The Chinese conceived of inoculation as a "transplant" of poxy material imagined as being like beansprouts which were just germinating. "To inoculate" in Chinese was called zhong dou or zhong miao, meaning "to implant the germs", or "implant the sprouts".

The method used was to put the poxy material on a plug of cotton, which was then inserted into the nose. The pox was thus absorbed through the mucous membrane of the nose and by breathing. (The technique of scratching the skin and putting the pox on the scratch seems to have developed long afterwards, possibly in Central Asia as the technique spread westwards.)

Ideally, inoculators chose poxy material from persons who had been inoculated themselves and had developed a few scabs. They also knew the difference between the two types of smallpox, Variola major and Variola minor, and they chose material from the latter, which was a less virulent form. Indeed, the favourite source of material was from the scabs of someone who had been inoculated with material from somebody who had been inoculated with material from somebody who had been inoculated... In other words, a several-generations attenuation of the virus through multiple inoculations.

But there were other artificial methods used to attenuate the virus even further, so that it would be safer still. Here is one account from a work on Transplanting the Smallpox by Zhang Yan in the year 1741:

"Method of storing the material. Wrap the scabs carefully in paper and put them into a small container bottle. Cork it tightly so that the activity is not dissipated. The container must not be exposed to sunlight or warmed beside a fire. It is best to carry it for some time on the person so that the scabs dry naturally and slowly. The container should be marked clearly with the date on which the contents were taken from the patient.

"In winter the material has yang potency within it, so it remains active even after being kept from thirty to forty days. But in summer the yang potency will be lost in approximately twenty days. The best material is that which had not been left too long, for when the yang potency is abundant it will give a `take' with nine persons out of ten; but as it gets older it gradually loses its activity, and finally it will not work at all. In situations where new scabs are rare and the requirement is great, it is possible to mix new scabs with the more aged ones, but in this case more of the powder should be blown into the nostril when the inoculation is done."

Needham comments on this and similar passages:

"Thus the general system was to keep the inoculum sample for a month or more at body temperature (37 [degrees]C) or rather less. This would certainly have had the effect of heat-inactivating some 80 per cent of the living virus particles, but since their dead protein would have been present, a strong stimulus to interferon production as well as antibody formation would have been given when inoculation was done."

In other words, 80 per cent of the smallpox viruses with which the Chinese were inoculated would have been dead ones which could not have given anyone smallpox. Instead, they would (as with vaccination) have stimulated the body to produce antibodies against smallpox.