The city tested practically its entire population of 18.7 million between Sunday and Tuesday, some of them for the second time. It has also put neighborhoods with a total of more than 180,000 residents into total lockdowns, with practically no one allowed out except for medical testing.
The early infections appear to have jumped from person to person at a cluster of eateries. Each infected person has infected more other people than in any previous outbreak that China has confronted, Zhang Zhoubin, deputy director of the Guangzhou Center for Disease Control, said at a news conference.
At home, China’s leaders are pushing its people to get vaccinated. It has administered about 800 million doses by the government’s count, compared with 300 million administered in the United States. Yin Weidong, the chairman and chief executive of Sinovac Biotech, one of China’s main vaccine manufacturers, told state television last Friday that Chinese regulators had approved the emergency use of vaccines in children as young as 3.
Still, administering 800 million doses — almost all of the vaccines require two shots — means most of China’s 1.4 billion people have not been fully vaccinated. Some people remain hesitant to get the shots, and Chinese media outlets have used the Guangzhou outbreak to encourage skeptics to get inoculated.
The Delta variant now circulating in Guangzhou has also shown the ability in other countries to infect some people who had already been vaccinated, a phenomenon known as vaccine escape. Research elsewhere has found that to be a particular problem for people who have received only a first injection of a two-jab vaccine and are then exposed to the Delta variant.
Researchers in Britain have found that receiving only the first of two shots of the Oxford-AstraZeneca or Pfizer-BioNTech vaccines may be only 30 percent effective in preventing infection with the Delta variant, said Raina MacIntyre, who heads the biosecurity program at the Kirby Institute of the University of New South Wales in Sydney, Australia.
After two doses, effectiveness appears to rise to 60 percent with the AstraZeneca vaccine and 88 percent with Pfizer-BioNTech. “With the degree of vaccine escape there is with the Delta variant, you really do need people to be fully vaccinated,” she said.