[Thermostability and immunogenicity of trivalent oral poliovirus vaccine produced by different countries].

Hep-2 cell-based microtiter assay system was used to test the titer of TOPV(Sabin strain). Before immunization, the overall potency results of TOPV produced by China, Yugoslavia, and Belgium were 6.38, 6.25, and 5.75 log TCID 50/0.1 ml, respectively. After storage at 37 degrees C for 2 days or after 5 cycles of freezing and thawing, the overall titer of each TOPV reduced less than 0.5 log TCID 50/0.1 ml. A randomized study was conducted in Anhui Province to test the serological difference among the TOPV which were produced by China, Yugoslavia and Belgium. The formulations of the TOPV produced by China and Yugoslavia were 6.0, 5.0, and 5.5 log TCID 50/0.1 ml of Sabin types 1, 2, and 3, respectively. All of the children in this study were divided into three groups, and children in group A, B, and C received TOPV produced by China, Yugoslavia, and Belgium, respectively. Three doses of TOPV were given to the children in the group at 2, 3, and 4 months of age. The seroconversion rates and geometric mean titers had no significant differences among these groups before immunization. At the end of one month following the 2nd dose, the rates of seroconversion to type 1-3 poliovirus in group A, B, and C were 88%, 98%, 98%; 92%, 98%, 92%; 100%, 100% and 96%, respectively. The rate of seroconversion to type 1 poliovirus in group C was higher than those in group A and B.(ABSTRACT TRUNCATED AT 250 WORDS)