Western politicians have faulted China for initial delays in providing information as the coronavirus spread around the world. Now as Beijing develops a vaccine, the need for transparency is proving essential to win back trust.

American drugmaker Pfizer Inc. and German biotechnology firm BioNTech SE announced this week that their vaccine appears more than 90% effective in stopping COVID-19 infections. The preliminary finding spurred a global stock rally and put the companies at the head of the pack in the race for the vaccine.

At around the same time, China saw the final-stage trial of one of its top vaccine candidates halted in Brazil due to a serious adverse event. While Brazil reversed its decision in less than 48 hours, the episode underscored the fraught geopolitical tensions around vaccine development: Last month, Brazilian President Jair Bolsonaro said China lacks credibility and people wouldn’t feel safe with the shot "due to its origin.”