In Rome University’s Orthopedic Clinic, 1,133 polio experts from 49 nations gathered last week, but the vital question —how good is the Salk vaccine? —was not even on the agenda. Although masses of statistics and case reports on the vaccine trials (TIME, March 29) are piling up, no conclusive answer can be culled from them until next year. Meanwhile. Dr. Jonas E. Salk reported to his colleagues in Rome, he has already gathered new data that will dictate changes in any future attack on polio with a vaccine similar to his.
It may be necessary to pick different strains of virus to represent the three main polio types because some highly infectious strains are less potent than seemingly milder strains when it comes to stimulating the production of protective antibodies. Also, individuals differ in their antibody response to vaccination, depending on whether they have had some previous natural immunity to one type of polio virus.
Most significant were Dr. Salk’s new views on how many vaccine shots should be given, and at what intervals. This year’s big field trials comprised three shots within a total of five weeks. But, said Dr. Salk, his latest research has made it clear that in man the best interval is more than five weeks—just how long Salk cannot yet say. After this period is determined, he hopes to be able to confer lifelong immunity against polio with only two inoculations.
The cautious U.S. Public Health Service allowed itself a well-qualified prediction: the 1954 polio season should decline in severity from now on, as it apparently reached an early peak at the end of August. The last three weeks for which full U.S. figures were available showed 2,206 cases, then 2,210 and a drop to 2,105. Total cases for the calendar year so far: 19,215, as against 20,325 in 1953, and 27,209 in 1952.
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