"After two doses of Xinguan vaccine are vaccinated, the third dose should be replanted in time." on the evening of November 11, the plenary meeting of the global Mayors Forum opened in Guangzhou. Zhong Nanshan, academician of the Chinese Academy of engineering, delivered a keynote speech on "characteristics and prevention of delta variant infection in Guangzhou Xinguan", he said, "Whether whole virus inactivated vaccine or mRNA vaccine, the humoral immune function decreased significantly half a year after a course of treatment. Countries are exploring how to strengthen immunity." At the scene, Zhong Nanshan showed the data released by the Ministry of health of Chile on October 7 this year. The data showed that after Kexing strengthened immunization, the protective effect was enhanced, the protective effect on symptomatic new crown cases was increased from 56% to 80%, and the protective effect on hospitalized cases was increased from 84% to 88%. In Zhong Nanshan's view, the current problem of epidemic prevention and control lies in balance. On the one hand, restart the economy and on the other hand, control the epidemic. "This requires precise prevention and control." he said, but he also stressed that precise prevention and control does not mean adding weight at all levels. Too much will affect economic development. When can we restore normality? Zhong Nanshan believes that full openness can be achieved on the premise of controlling the virus mortality at 0.1%, the replication index at 1.0-1.5 and reducing the transmission coefficient. However, to achieve these prerequisites, we need to take measures such as universal vaccination, establishing mass immunization, normalizing community mass prevention and control, and developing effective drugs. Among them, the generation of group immunity depends on two ways. One is to adopt infection without interference, that is, natural infection, but 70% - 80% of the population needs to be infected. According to the mortality rate of 2.1%, the number of deaths in the world will reach 12.64 million through natural infection. Zhong Nanshan said that this way is unrealistic, unscientific and inhumane. Another way to achieve mass immunization is mass vaccination. Even if most people have immunity, so as to curb the spread of infectious diseases, it takes 2-3 years of global cooperation. As of November 9, 1073 million people in China have completed the whole process vaccination, 41.713 million people have completed the enhanced vaccination, and the data in Guangzhou is 17.321 million people, accounting for 92.7% and 836000 people Received intensive vaccination. He also mentioned that when the delta mutant appeared in Guangzhou in May this year, none of the patients who had been vaccinated were seriously ill. Guangzhou also took many effective measures against the characteristics of short incubation period and fast transmission speed of delta mutant. Later, there was an epidemic all over the country, and Guangzhou's practice was also referred to. Zhong Nanshan introduced Guangzhou's experience in dealing with delta mutant strains, including: updating the concept of "close connection", formulating closed and sealed control modes for delta virus classification; adopting the "yellow code" system, identifying people who have been to high-risk areas through big data, giving the "yellow code" mark, and requiring to complete nucleic acid detection as soon as possible and increase the nucleic acid detection frequency of "yellow code" personnel; building a The "Falcon" gas film laboratory carried out large-scale rapid screening; the construction of Guangzhou international health station provided a smart and safe isolation area. Under a series of measures, the transmission index of delta mutants in Guangzhou continued to decrease. "If a corner is disturbed, the whole world is in danger." Zhong Nanshan once again stressed that the epidemic prevention and control must not be relaxed. (outlook new era)