Southeast Asian countries that had widely rolled out Chinese-made coronavirus vaccines are turning away from the shots in favor of Western alternatives as they scramble to contain deadly outbreaks caused by the delta variant. The shift in a region where China vies with the United States for influence underscores the limits of Beijing’s vaccine diplomacy. Countries such as Indonesia and Thailand once bet heavily on China’s Sinovac, despite warnings from medical experts, but their health systems have come under intense strain as the delta variant tears through towns and cities. Indonesia has recorded more than 100,000 deaths overall.

“The current reality does present a stark contrast to the fanfare with which Beijing rolled out their vaccines and then insisted on their high efficacy, even when data was less available,” said Chong Ja Ian, an associate professor of political science at the National University of Singapore who studies U.S.-China competition in Asia. The change, he added, shows “how risky it is to try to make the current pandemic, and the very real dangers to human life, into a sort of propaganda tool.”

Sinovac and Sinopharm were among the earliest to begin clinical trials, but they did not release full data. Millions of people have taken the shots, which governments rushed to procure amid supply constraints before the United States pledged to share doses. With wealthier nations snapping up Pfizer and Moderna, some developing countries had little choice but to look to China. Doubts over Sinovac’s efficacy grew in June, when fully vaccinated Indonesian doctors began dying of covid-19. The Indonesian Medical Association has recorded at least 20 deaths of doctors who were doubly dosed with Sinovac. Earlier that month, the World Health Organization approved the vaccine for emergency use.