The Salk Verdict

The scientific courts judging the Salk polio vaccine have had an exasperating way of reversing themselves. Now it's safe, now it isn't. Now it works, now it doesn't quite. In Kansas City last week, 6,000 members of the American Public Health Association listened to further testimony on how effective the Salk vaccine proved itself in last summer's mismanaged mass inoculations.

The verdict was that the vaccine was generally safe and effective. Normally cautious Epidemiologist Alexander Langmuir of the U.S. Public Health Service reported, on the basis of returns from eleven states plus New York City, that the vaccine had been 75% effective, or better, in preventing paralytic polio among children in the five-to-nine age group, even though many had received only one or two inoculations instead of the desired three.

New York State (outside the city), with a massive 450,000 children inoculated, had telling figures: the paralytic-polio rate among the unvaccinated was 21 per 100,000, but only four per 100,000 among the vaccinated. In nonparalytic polio, the protection ratio was only about 3 to 2, but final returns were expected to show that the disease had been milder, on the average, in vaccinated children. Chicago was unofficially reported to have had only two cases of paralytic polio per 100,000 among the vaccinated, as compared with 32 among the unvaccinated.

Eastern Mystery. Dr. Langmuir was forthright in listing cases where something went wrong. Among those who got vaccine made by California's Cutter Laboratories, 79 developed polio; so did 105 members of their families and 20 "com munity contacts." Three-fourths of the cases were paralytic; there were eleven deaths. Vaccine from a second manufacturer, Pennsylvania's Wyeth Laboratories, was suspected of responsibility for an unstated number of polio cases in the East, but the most rigorous testing by the federal Division of Biologic Standards failed to demonstrate live virus. These cases remained a disguieting mystery.

The PHS's Surgeon General Dr. Leonard Scheele then read a report by his technical committee on the most recent steps to make the vaccine safer. There were "striking differences," said Scheele, in "the degree of clarity of the different fluids" from which the various manufacturers have prepared vaccine. After the virus is grown in a broth of monkey-kidney tissue and left standing, a sediment may appear at the bottom of the flasks. The sediment is like lumps in porridge. When formaldehyde is added to kill the virus, it cannot reach the particles in the middle of the lumps, thus leaving them dangerously infective.

In some cases, said Scheele, manufacturers had left virus cultures lying around for months and had failed to filter them before adding formaldehyde. Why this was permitted he did not say. Now, filtering must be done within 72 hours before the virus is killed and with the finest of glass filters.

Precipitate Close. Later in the week, 1,000 delegates crowded to hear a panel of twelve polio experts, among them Jonas Salk himself, discuss their experience with the vaccine. Dr. Salk offered evidence that children under six can get as much protection from the vaccine as their elders--which some of his critics doubt--and defended continued use in the vaccine of the Mahoney virus strain, a potent cause of paralysis.

The upshot of five days of polio-oriented meetings: the Salk vaccine is good, but as used this year it was imperfect, and its boosters seem determined to keep the public (which paid more than $35 million for it) from learning much about those imperfections. Next year's prospect: 50 million or more doses of vaccine will be available (how many people will get how many shots is still to be decided); the vaccine will be safe; and it will be at least 80% effective.

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