Live Virus in the Jungle

Many experts are convinced that the best possible vaccine against paralytic polio would be one containing live virus --it is cheaper to give, easier to take (by mouth) and should be more potent. But U.S. health authorities are fearful that some virus might prove to be not only live but virulent. They play it safe with the Salk vaccine, in which the virus is killed with formaldehyde. Now, from darkest Africa, comes the report of a trial in which a quarter-million people have been given a live-virus vaccine made in the U.S. It appears to have been completely safe, almost 100% effective.

Moving spirit behind the test was Dr. Hilary Koprowski of Philadelphia's Wistar Institute. To combat epidemics of paralytic polio in the Belgian Congo, he got World Health Organization backing and Congo government funds, arranged a mass trial. Wistar Institute brewed big batches of two strains of polio virus: Chat (named from the initials of the child from whom it was taken), belonging to Type 1, and Fox III (named for a doctor who isolated it from a child victim), belonging to Type 3. Both strains were attenuated, i.e., they were grown in different media (including mice) until they lost all power to cause paralysis, though they could still stimulate the human system to produce antibodies. Both were tested in human volunteers in the U.S. before shipment to Africa, where they were again checked for safety in chimpanzees at a specially established animal farm.

Type 1 virus was causing most of the Congo's paralytic polio, Koprowski and colleagues found. They gave the Chat strain in capsules to 1,978 schoolchildren, found that none got sick, and all but two developed good antibody protection. It was exactly the same later with Fox III --all but two of the children responded well. The researchers were ready for a truly big-scale test.

They moved into the valley of the Ruzizi River, boundary between the U.N. trusteeship of Ruanda and the Congo proper. Working both sides of the stream, they got native chieftains to pass the word by jungle telegraph. At their chieftains' bidding, 215,504 men, women and children trooped down to rally points where the doctors were waiting with jugs of ice-cold Chat. In some cases, team members squirted the virus-containing liquid into the tribesmen's mouths; usually, they let them take it from a tablespoon. There were no ill effects, and team members have high hopes that they averted a lot of polio.

In other areas live-virus vaccinations were begun after an epidemic of paralytic polio (Type 1) had already broken out. Each time Chat seemed to check the outbreak: not a single paralytic case was reported after the immunization teams had done their work.

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