Virologist Shan-Lu Liu from The Ohio State University in the United States said that as vaccine protection waned, reinfection rates would rise.

“China will likely follow the trend, and repeat infection waves as seen in other parts of the world,” Liu told The South China Morning Post, saying Omicron – the dominant variant around the world for more than a year – had the highest rate of reinfection.

Scientists are still trying to understand the basics of why some people who recover from Covid-19 become infected again.

“At this point, it seems difficult to prevent such situations from happening in China,” Peking University biochemist Cao Yunlong told state-run China News Service on Wednesday.

In a study led by Peking University, researchers examined 6.6 million cases from around the world and found the average reinfection rate of all pre-Omicron variants was around 2 percent.