What Is It?

Six big U.S. pharmaceutical firms* are now producing Salk vaccine or hurrying to get into production. The vaccine works on a principle that has already provided protection against such traditional plagues as smallpox and yellow fever. When they attack human beings or other mammals, most viruses stimulate the invaded system to manufacture tiny protein particles "called antibodies. If the system under assault does not have enough of these antibodies, or cannot manufacture them fast enough, the victim may die, or, with polio, suffer permanent crippling. Polio virus is unusual in that there are three main types. All can cause paralysis, but one type causes more than the others combined. Within each type there are many different strains. The Salk vaccine is made by taking a representative strain of each type and growing it--till it reaches many times its original strength --in a broth made with snips of monkey kidney. (To keep production going, 4,000 monkeys a month are flown in from India and the Philippines.) Then the virus in each deadly brew is killed with formaldehyde. Strangely, although the virus particles now lose their power to multiply or to cause disease, they keep their power to stimulate a higher animal to produce antibodies. Because in the Salk formula the virus types are mixed, the Salk vaccine is really three vaccines in one, effective against all known polio strains.

* Cutter Laboratories, Berkeley, Calif.; Eli Lilly Co. and Pitman-Moore, Indianapolis; Parke, Davis & Co., Detroit; Sharp & Dohme and Wyeth Laboratories, Inc., Philadelphia.

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