Next: Live Vaccine?

While virologists were still trying to decide whether Dr. Salk's "killed" virus vaccine was safe, or how it could be made safer (see above), other experts argued that the killed-virus idea should be abandoned altogether. Leader of this school:

Russian-born Dr. Albert Sabin, 48, director of Cincinnati's Children's Hospital Research Foundation. His alternative: instead of killing a virulent virus, use a living virus that is nonvirulent to begin with.

Short or Long. To buttress his arguments--that a live virus is better and confers longer immunity--Researcher Sabin went to the Eskimos. In one of their isolated communities immunity against polio was shown to have endured for 40 years after the last previous encounter with the virus. Use of the short-term killed vaccine, argues Sabin, might leave U.S. parents with the necessity of having their children reinoculated every year or so.

Graver still was the fact that polio is likely to be more serious the older the victim. If children are protected by a series of short-term immunizations, they might grow into young adults with no lasting immunity and a dangerous susceptibility to paralytic polio.

But is the live vaccine safe? Dr. Salk, for one, does not think so. Although the live-virus method has been used successfully in the long-established smallpox and yellow fever vaccines, he believes that the polio virus is too tough and tricky to permit development in safe, nonvimlent form. Dr. Sabin disagrees, thinks it can be done. Growing virus strains of all three types under hothouse conditions, he found some that, when injected into the spinal cords of chimpanzees, produced no paralysis. All they did was to stimulate the animals to produce antibodies against any future invading polio virus. And these antibodies were, Dr. Sabin said, more abundant and effective than those generated by a killed vaccine.

Only Setback. For human subjects he chose Ohio's Chillicothe Federal Reformatory. Of 30 volunteers (between the ages of 21 and 30), 26 got a minute droplet of a single strain of polio virus in a teaspoon-ul of milk. The human guinea pigs proved even more susceptible than the chimpanzees to the desired kind of infection. They did not get sick in any apparent way Yet the virus multiplied in their digestive tracts, boosted their antibody levels and was excreted in the stools for one to twelve weeks. It was in this connection Dr. Sabin reported his only setback :

some of the virus changed in the subjects' bodies to a somewhat virulent form.

Taking a long leap into a hypothetical future, Dr. Sabin foresaw a day when babies will have their throats swabbed with his vaccine before they are six months old, while they are still protected by inherited antibodies. Or, others sug gest, people of any age could get tem porary immunity from a single Salk shot then parlay it into virtual lifetime immunity with a Sabin swab.

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