More work is going into a syphilis vaccine than into one against gonorrhea, but, as Dr. John Knox put it in 1969, "more money is being spent to eliminate athlete's foot than syphilis." The technical difficulties are not the same as for gonorrhea. The spirochete of syphilis, as you know, cannot be cultured predictably or in virulent form either by methods used for bacteria, in soups or jellies, or in developing hens' eggs or the tissue cultures cultures in glass of cells from man or animals used for viruses. Treponema pallidum grows only in the tissues of man or of a few species of living animals. Lack of the usual culture methods is a serious drawback to vaccine development. Just the same you may remember that the very word, vaccine (Latin vaccus, "cow") relates back to the use by Edward Jenner in the last years of the eighteenth century of cowpox material for inoculation against smallpox, long before cultures were dreamt of. So, while the hope of growing the spirochetes in culture has not been abandoned, work toward a vaccine goes forward mainly along other lines, using spirochetes from experimental animals.

One of the advantages of cultures is that they can provide large quantities of the bacterium. Large quantities are needed to separate the bacterial substance the intended antigens from contaminating antigens that might cause allergies and other unintended effects. But other ways can be found to accomplish these ends. Members of the VD research group in Atlanta have been cooperating with workers at the atomic energy laboratories at Oak Ridge, and by using newly developed special large scale equipment have been able to prepare a sizable batch (13 liters, which is nearly 3 ½ gallons) of extract of spirochetes from rabbit testicles, from which they made a purified immunizing agent for rabbits.

In one respect syphilis conforms to the disease pattern which encourages an effective vaccine: the spirochetes are in the blood very early in the course of the disease, possibly early enough to prevent even the chancre if the effective antibody level were high enough.

Usually we think of immunity against infectious disease as something that follows recovery from the disease. But in syphilis, although recovery without treatment may happen in something like one out of four cases, it is unpredictable in the individual patient. We usually expect somebody with an infectious disease either to get well or to die; but the latent syphilitic can live for many years without knowing that the disease will not reappear. (see THE POSSIBILITY OF A VACCINE FOR SYPHILIS PART II)