Unpredictable changes in the microscopic world of the coronavirus worry the world's scientific community. They pose an ongoing challenge in the fight against the pandemic the virus has caused. At the same time, equitable global access to COVID-19 vaccines has to be ensured if a global immunity barrier is to be built. To cope with this situation, China has been committed to making vaccines a global public good and fulfilling international vaccine assistance obligations while satisfying its domestic demand. Episode 2 of the series "Racing Against the Coronavirus" provides an in-depth view into China's efforts toward making the global wall of immunity a reality.