Evaluation of Sabin Live Poliovirus Vaccine in Japan

Two methods of administration of Sabin vaccine were investigated in 474 infants mostly 0 to 8 months of age, with two levels of dose, 105.0 and 106.0 TCID50. In Method 1, monovalent type 1, divalent types 2 and 3, and trivalent vaccine, were administered in this order, and in Method 2, trivalent vaccine was given twice; the interval between consecutive feedings was 6 to 8 weeks, Immunization at the age of 3 months or later by Method 1 was shown to be most effective and, in this case, 105.0 TCID50 dose was as satisfactory as 106.0 TCID50 dose. The most suitable time for the first feeding of vaccine is considered to be about 3 months after birth. In spite of inferior effectiveness to Method 1, Method 2 is considered to be practically satisfactory enough in infants over 3 months of age, particularly so because the method is less complicated.