Evaluation of Seroconversion in Guinea Pigs Following Inoculation of New Formulations of Rubella Vaccine

Rubella is a contagious viral disease mostly with mild clinical symptoms and often remains undiagnosed. Rubella infection may adversely affect pregnancy, especially in the first trimester and this mother to child transmission can cause congenital rubella and may be lead to permanent disability and mortality in children. Effective rubella vaccine should be prepared using suitable stabilizers. New stabilizers should be selected carefully in the manners that final product meet all requirements of stability, immunogenicity and safety. The aim of this study was to evaluate the immunogenicity of rubella vaccines that are formulated using two different new stabilizers in comparison to a commonly used vaccine that gelatin is used in it as a stabilizer. 28 guinea pigs were prospectively divided into four groups (one control and three test groups) according to the materials that they were subjected to receive, including the vaccines that formulated with hydrolyzed gelatin (G), Sorbitol (S) and Trehalose dehydrate (T) stabilizers. Control group was received sterile water for injection (WFI). Anti-rubella antibodies in the sera were measured using haemagglutination inhibition (HI) technique. The results were analyzed by Generalized Estimating equations (GEE) statistical test. Our results showed that all three formulated vaccines (G, S and T) induced seroconversion in guinea pigs; however the vaccine that contained Trehalose dehydrate (T) induced a slightly higher level of antibody against rubella virus (p<0.01). As an important part of final bulk of rubella vaccines, stabilizers are continuously studied to achieve safer, more stable and more effective vaccines. In this study, the immunogenicity of newly formulated rubella vaccines (T&S) was comparable to the vaccines which formulated with routine stabilizer (G).