Can a Covid Vaccine Be Too Perfect?

The lack of serious side effects in China’s big trials is raising concerns about transparency

- By Rachel Chang, Michelle Fay Cortez, and Anjali Cordeiro, with Jinshan Hong and Riley Griffin

Chinese companies’ seemingly remarkable progress has them leading the race for a coronavirus vaccine. Their speedy ascent has been unhindered by common scientific setbacks being reported by Western rivals, however, raising questions about how stringently they’re vetting results and reporting potential safety issues.

China has the largest number of candidates in late-stage vaccine trials, and its shots could be used by millions worldwide because President Xi Jinping has pledged to share successful ones overseas. But there is concern about Chinese developers’ standards and safeguards because some of their vaccines are being distributed in the country under an emergency use program before getting full regulatory approval.

AstraZeneca Plc and Johnson & Johnson temporarily halted testing earlier this year in the U.K. and the U.S., respectively, after a single participant in each trial got sick. In contrast, China’s science ministry has said its companies have inoculated about 60,000 volunteers in final-stage trials, but there have been no reports of serious adverse events.

One front-runner, China National Biotec Group Co., has said it’s vaccinated hundreds of thousands of people under the emergency use program, a sign of how widely Chinese shots are being administered without reports of serious adverse events. Yet scientists say the discovery of health problems is inevitable when so many people of all ages and with varying conditions are tested—even if the vaccine isn’t causing the illness.