Salt Process Delays Lots New York Times Service WASHINGTON, Jan, 29 - The difficult process of producing and testing Salk vaccine makes it improbable that the 54 million persons in the present priority group will be immunized before next summer. This group includes children from birth to 15 years of ae and all pregnant women. Originally the age-group given priority by the National Advisory Committee on Polio Vaccine was 5 to 9. WHEN LARGE numbers of these children had received first shots, the committee broadened the priority. When the “under 15” program is pretty well complete, the priority will be extended to age 20. This extension would raise the total number in the age group to be vaccinated to 65 million. Surgeon General Leonard Scheele of the Public Health Service said he is hopeful this can be done by June 30, 1957 when the federal program of sending vaccine free into the states will have been completed. SO FAR 30 million dollars has been appropriated for this program. It expires Feb. 15. The administration is seeking extension of this legislation and another 30 million dollars.