Immunogenic Potency of MgCl2—Stabilized Oral Poliovaccine

IN ALL PARTS OF THE WORLD, oral polio-virus vaccine is widely accepted as an effective immunizing agent.¹The vaccine is a living, attenuated virus, and like most viruses it is unstable, except when held at very low temperatures in the frozen state. As a result, present regulations and practice in this country require that for maintenance of potency the vaccine be stored and shipped frozen, and that after thawing it be held in the refrigerator at no more than 10 C for a period not to exceed 7 days, after which time it must be discarded. Recent findings have shown that polio and other enteroviruses, in contrast to most other viruses, are rendered thermostable in the presence of high concentrations of MgCl₂.², ³This report describes comparative results of feeding children ordinary nonstabilized poliovirus vaccine, stored under optimal conditions (—20 C), with results of feeding MgCl₂