Note: Respond To All Questions Below What observation did Jenner base his vaccin

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What observation did Jenner base his vaccine hypothesis on? In other words, what information did he have going into his smallpox experiments that led him to believe that thev actually work? th smallpox it was not at all understood what the cause of the disease was, except that the cause seemed to be something medical professionals called "the smallpox poison." That phrase, usually referred to in its Latin form, variola virus, meant literally "the smallpox poison," and was said to be the cause of smallpox (variola). The term "virus," in the centuries before Louis Pasteur (18221895) and Robert Koch (18431910) with their discoveries of microbes as the causes of infectious diseases, was used only to mean the generic notion of "some poisonous force." The was that no one knew just what caused smallpox. (Those today who criticize the HIV-causes-AIDS thesis would say that today also we do not know fully what the cause of AIDS is; they then conclude from this that we should therefore not be looking for an HIV vaccine, since we do not know that HIV is the cause of AIDS.) To make matters worse, the pathogenesis of smallpox, i.e., the physiological mechanism(s) by which the poison" caused disease in the body, was also not understood. Microbiology, after all, would not come into its own until late in the 19th century; physicians in the 18th century, therefore, had no way of knowing that some microbes (which they didn't even know existed) grew inside bodies and made them sick. Most AIDS researchers today also candidly acknowledge that we do not fully understand the pathogenesis of HIV disease and AIDS, and that there is still much research to be done on this matter. And yet, in spite of these two deficiencies - i.e., in spite of understanding neither the causal agent of the disease nor the pathogenesis of the disease there was still a clearly focused effort on the part of one man (an ultimately successful concerted effort) to discover a method of artificially inducing an immunity to smallpox. That is, despite these serious lacunae in the understanding of smallpox, the search for a technique that would safely and effectively immunize persons against the ravages of smallpox was ultimately successful. This realization should probably buoy the sometimes lagging spirits of those who hope to find an HIV vaccine that will successfully immunize persons against AIDS and other HIV disease. Of course, the discovery of an artificially induced smallpox immunity (a vaccine) came about only after, and as a result of, the clear recognition of the existence of an already naturally-occurring immunity to smallpox, i.e., an immunity acquired by actually contracting the disease naturally. So far today with AIDS we do not have any clear, convincing evidence of a pre-existing, naturally-occurring immunity (though there are some promising possibilities already being explored) Almost everyone (> 90%) who becomes infected with HIV seems to eventually get sick and die of AIDS or other HIV disease. On the other hand, however, it may not be entirely true that we have no cases of naturally-occuring immunity to HIV. Long-term survivors of AIDS, and/or1 term non-progressors (i.e., persons whose HIV infection does not seem to progress toward disease), may tum out to be persons who are naturally immune to AIDS. Or it may even turm out to be the case that virtually everyone who becomes infected with HIV - during their first several years simple fact f infection, when the virus is living and replicating (apparently very prolifically) in the body without causing any clinical disease - will turn out to be an example of a naturally-occurring immunity. This possibility has been hinted at in recent studies which indicate that the immun successfully battles HIV for the first several years, generating two billion new T-4 cells every day to eliminate HIV from the body. The onl;y reason, say these studies, that the infection progresses so slowly is that the combatants - HIV and the immune system - are so closely matched Any of these instances, or perhaps another one not yet discovered, may turn out to be the example of naturally-occurring immunity on which will be based the discovery of a successful AIDS vaccine. In any case, despite significant differences between smallpox and AIDS (e.g., their modes ftransmission, latency periods, effect on the immune system, etc.), there are a number of interesting similarities. One similarity, for example, is that the origin of both diseases in humans is uncertain, but both seem to have probably originated in animals and then crossed species to humans (Cowpox, swinepox, monkeypox, and rabies are examples of other diseases that have also crossed species to humans.) The rapid spread of both diseases throughout the world came about, at least partially, as a result of changes in global transportation pattems. Both diseases are viral in origin. Both diseases are felt, with good reason, to be the most serious plague of their epoch. Both diseases cause severe morbidity. Both diseases have serious lifelong consequences. Both diseases have a high mortality rate. Both diseases lead to severe social stigma. Persons suffering from both diseases are (or were) socially shunned. Neither disease is curable, given the contemporary state of medical science. And in the case of both diseases, experiments were (or are being) proposed which try to protect people against contracting the disease by means of inoculating them with the exact same agent that seems to cause the disease. Taking note of these intriguing similarities between smallpox and AIDS, despite all the differences between them, may prove to be instructive. It may also provide something of an antidote to the threatening sense of dejection, almost bordering on hopelessness, that sometimes challenges those who hope to someday find a vaccine against this terrible disease. Smallpox, after all, is the one disease that the human race has completely eradicated|

Explanation / Answer

Dr. Edward Jenner observed that milkmaids were immune to smallpox. He postulated that the pus in the blisters that milkmaids received from cowpox, protected them from smallpox. Based on this hypothesis, he performed his first vaccination on James Phipps on 14 May 1796.

Dr. Jenner scraped pus from cowpox blisters on the hands of Sarah Nelmes (a cowpox affected milkmaid) and inoculated inoculated James Phipps. Phipps showed symptoms of fever, but was not affected with the disease. Later, even after testing with small pox causing agent, phipps did not show any sign of infection.

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