Calling the Shots

Although the Salk vaccine against poliomyelitis has been generally effective --saving hundreds of lives and preventing thousands of cases of paralysis in four years--much of the material used in about 200 million U.S. inoculations has been no good. As a result, an all-out effort to improve the commercially produced vaccine is now being made. Until this succeeds, individuals who have already had three injections should get a fourth.

This was the word last week at a University of Michigan symposium with which the National Foundation launched its 1959 March of Dimes. Vaccinventor Jonas Salk was more frank than ever before in conceding the ineffectiveness of an unspecified proportion of the commercial vaccine released, and contrasting it with the small batches made in his University of Pittsburgh laboratory. Dr. Salk has always stoutly insisted that his handmade vaccine was capable of doing everything expected of it, and among hundreds of children inoculated with it there have been few cases where it failed to "take." Lat since wholesale vaccinations began in 1955, overall effectiveness of no more than about 80% in preventing paralytic polio has been claimed (many cases of paralysis have been reported in children who had had three shots).

Beef It Up. This kind of trouble is unavoidable with any killed-virus preparation, but was intensified in the case of polio vaccine early in the 1955 vaccination season when about 200 cases of polio were blamed on infective vaccine. The U.S. Public Health Service and the manufacturers understandably redoubled their efforts to make the vaccine safe. They succeeded--there has been no such disaster since--but at the cost of an equally desirable increase in the vaccine's potency.

The idea that many people do not respond to the vaccine is wrong, Dr. Salk reported on the basis of elaborate studies; such people are few. This knocks out the usual excuse for the commercial vaccine's failures. So the mass-produced vaccine must be beefed up to the potency level of his laboratory brand. But Dr. Salk also conceded defects in the design of the vaccine itself. It contains three strains of polio virus for the three broad types that can independently cause disease-- Mahoney for Type I, MEF-1 for Type II. and Saukett for Type III. About 80% of paralytic polio used to be caused by Type I strains; of the balance, Type III caused slightly more than half, leaving Type II as the least dangerous. But it is against Type II disease that the vaccine has proved most effective--it has almost disappeared in four years. The explanation is in the antibody levels that Dr. Salk has studied in the children he inoculated: highest against Type II, lower against Type I and lowest against Type III.

Booster Now. Other symposium speakers agreed that the most urgent next step in the anti-polio war is to complete three-shot protection for 50 million Americans under 40 who still have had no vaccine or only an odd shot. This will mean wiping out pockets of epidemic potential, now found mainly in low-living-standard areas, such as the Detroit slums that bred 1958's deadliest outbreak. Simultaneously, Dr. Salk recommended a fourth or booster shot for those who have already had three. (Though some nervous-Nellie parents have had their children jabbed seven or eight times, this apparently does no good: the fourth shot gives antibody levels as high as they can be pushed.)

Though Dr. Salk did not specifically propose it, a drastic revision of the vaccine seems inevitable, probably by replacing Mahoney and Saukett with better strains for Types I and III. Eventually, he was confident, paralytic polio can be prevented with only two shots of improved vaccine, with a third shot later to give "prolonged immunity."

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