On January 2, "XBB. 1.5 strain has been detected in Shanghai" was rushed to hot search. According to American media reports, the prevalence rate of this strain in the United States nearly doubled the previous week, accounting for about 41% of the current new cases in the United States. XBB. 1.5 has become the new "No. 1 virus" in the United States. It is reported that XBB. 1.5 detected in Shanghai is imported from abroad. With the adjustment of the nucleic acid testing policy and isolation requirements for China's entry personnel on January 8, will this strain cause a new wave of infection peak? XBB. 1.5 Under the background of mass immunization in the United States, the infection peak is still triggered. How should China deal with it? If XBB. 1.5 enters our society, will it trigger a new wave of infection peak? "Whether a mutant strain can defeat the existing strain depends on whether it has a more obvious advantage in transmission." Tong Yigang, a virologist and dean of the School of Life Science and Technology of Beijing University of Chemical Technology, told the Science and Technology Daily that XBB. 1.5 will compete with BF. 7 (or BA. 5.2) for a period of time after entering China, but new strains with transmission advantages in the United States will not produce the same results in our Congress, We can't be sure now. "The second wave of infection peak depends on two aspects, one is how much the new virus strains are similar to the epidemic virus strains, and the other is how the current population immunity level is." Tong Yigang explained that, on the one hand, although XXB. 1.5 is a new subtype, and there has been variation in key sites, neutralizing antibodies in the human body not only target one site of the virus, but there are a large number of neutralizing antibody epitopes (sites) on the surface of the virus, Other sites may also be blocked by antibody neutralization, so that the virus cannot infect human cells. Therefore, a large number of neutralizing antibodies produced by epidemic strains in human body still have certain neutralizing effect on new strains, which can also be said to be cross immune protection. On the other hand, in the newly formed peak of infection in China, many people's immunity formed through infection is at a high level. Due to the role of cross immune protection, there is little possibility of re infection in the near future. The relevant research results in the United States show that the median interval between the first infection and the second infection is 191 days. The median interval between the second infection and the third infection was 158 days. This data is basically consistent with the statement that the neutralizing antibody existed for 6 months. Previous research by Zhang Wenhong, director of the Infection Department of Huashan Hospital affiliated to Fudan University, also showed that antibodies in infected people after vaccination can also produce a very strong neutralizing effect on other variants. Zhang Wenhong believes that mixed immunization can construct immune barrier against various new mutants. Although XBB. 1.5 may not "step on the spot", many experts told reporters of Science and Technology Daily that the second wave of infection will still occur. "After the adjustment of the entry policy, various foreign strains of virus may come in." Tong Yigang said that COVID-19 exists objectively, and its "exploratory" variation also continues to exist. Once a mutation escapes most of the immune barriers in the human body, and it is easier to bind to the ACE2 receptor, it may trigger a peak of infection in a region. Just like playing the "dodgeball" game, COVID-19 has been mutating in the transmission