Evidence of Extended Thermo-Stability of Typhoid Polysaccharide Conjugate Vaccines.

Typhoid conjugate vaccines (TCV) are effective in preventing enteric fever caused by serovar Typhi in Southeast Asia and Africa. To facilitate vaccination with the Vi capsular polysaccharide-tetanus toxoid conjugate vaccine, Typbar TCV, and allow it to be transported and stored outside a cold chain just prior to administration, an extended controlled-temperature conditions (ECTC) study was performed to confirm the quality of the vaccine at 40 °C for 3 days at the end of its shelf-life (36 months at 2-8 °C). Studies performed in parallel by the vaccine manufacturer, Bharat Biotech International Limited, and an independent national control laboratory (NIBSC) monitored its stability-indicating parameters: -acetylation of the Vi polysaccharide, integrity of the polysaccharide-protein conjugate, and its molecular size and pH.