For more than a year, China had largely kept the virus at bay by tightly sealing its borders and swiftly taming local flare-ups with zero tolerance for infections. But despite stringent measures, a dozen cases of the Delta variant were detected among cleaning staff at one of the country's busiest airports. The variant soon spread to more than half of China's 31 provinces, resulting in excess of 1,000 infections in less than three weeks.
The rapid spread of Delta coincided with efforts to ramp up vaccinations. To date, 1.9 billion doses of domestic vaccines have been administered in China, according to the National Health Commission (NHC).