Typhoid conjugate vaccines (TCV) are effective in preventing enteric fever caused by Salmonella enterica 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: O-acetylation of the Vi polysaccharide, integrity of the polysaccharide–protein conjugate, and its molecular size and pH. ECTC samples stored at 40 °C and 45 °C in comparison with control samples stored at 4 °C and 55 or 56 °C, were shown to have stable O-acetylation and pH; only very slight increases in the percentage of free saccharide and corresponding decreases in molecular size were observed. The deoxycholate method for precipitating conjugated polysaccharide was very sensitive to small incremental increases in percentage of free saccharide, in line with storage temperature and duration. This extended ECTC study demonstrated minimal structural changes to the Vi polysaccharide and conjugate vaccine and a stable formulation following extended exposure to elevated temperatures for the desired durations. This outcome supports the manufacturer’s ECTC claim for the vaccine to be allowed to be taken outside the cold chain before its administration.

The Developing Countries Vaccine Manufacturing Network coordinated a multi-laboratory study funded by the US National Institute for Innovation in Manufacturing Biopharmaceuticals to assess the performance of the Pertussis Serological Potency Test (PSPT) in the laboratories of seven whole-cell pertussis vaccine (wP) manufacturers and three National Control Laboratories based in Southeast Asian countries. To this end, common protocols for the immunization of mice and serological testing by ELISA were shared with all laboratories. Each laboratory used their own wP vaccines and the reference vaccine routinely used in the regulatory required mouse protection test (MPT) and assayed the products both in the MPT and PSPT. Whereas in all laboratories the PSPT showed decreased serum IgG levels after immunization with sub-potent compared to potent final batches, some issues were encountered during execution of the assay, which prevented drawing of definitive conclusions on assay performance. Nevertheless, the study provided the participants with the opportunity to familiarize themselves with the PSPT protocols and revealed the next steps to be addressed for implementation of the method.