Popular science: What are the anti-epidemic enlightenments brought by the second infection of the new crown

Source: Xinhuanet

Hong Kong, China recently reported the world's first case of reinfection with the new crown virus. A 33-year-old man who was diagnosed with the new crown at the end of March recovered and was discharged from hospital. He was diagnosed again after returning to Hong Kong from a trip to Europe in August. Does repeated infection after recovery mean that even if the new crown vaccine is officially put into use, it will not really be able to overcome the epidemic? What lessons does this case bring to the prevention and control of the new crown epidemic? Experts believe that the case of secondary infection of the new coronavirus is not a routine event, and there is no need to worry too much. The significance of this case is to help researchers to better understand the body's immune response to the new coronavirus.

Different from the previously reported cases of "Fuyang", the newly reported cases of repeated infections provide for the first time conclusive evidence that patients recovered from the new crown may be infected again.

"Fuyang" refers to a positive nucleic acid test after a new crown patient reaches the discharge standard. Experts believe that the description of such cases as "re-detection" may be more accurate. The virus has not really been eliminated from the patient's body. Although the virus cannot be detected in the upper respiratory tract throat swab sampling, the virus still exists in the body. In addition, insufficient sensitivity of nucleic acid detection reagents may also bring about "false negative" results.

Researchers from the Department of Microbiology of the University of Hong Kong, Hong Kong Queen Mary Hospital and other institutions reported in the latest study published on the 25th in the authoritative international infectious disease journal "Clinical Infectious Diseases" that the second infection of this repeat infection occurred after the first infection. On day 142, comparing the two infected new coronavirus genomes, it can be found that they belong to different branches of the new coronavirus lineage, have more than 20 different nucleotides, and have amino acid differences in 9 proteins, confirming that the patient is re-infected. Instead of the first infection, the virus persists.

Previous studies have shown that the level of antibodies in the body of people infected with the new coronavirus will drop rapidly after they recover. The Chinese research team reported in the British journal Nature Medicine in June that their investigation in Chongqing found that about 90% of cases had a total antibody level drop of more than 70% two months after discharge. Based on this, researchers believe that people infected with the new coronavirus may be infected again after they recover. The newly reported cases of superinfection confirm the above conclusions, indicating that people infected with the new coronavirus may not be immune for life.

Does this mean that even if the new crown vaccine is officially put into use, it will not truly be able to overcome the epidemic? Experts said that from the perspective of the population, secondary infections of the new coronavirus are extremely rare and will not have a major impact on the realization of immunity through vaccination. World Health Organization spokesperson Margaret Harris said on the 25th that only one secondary infection has been found among the more than 23 million confirmed cases of new crowns worldwide, indicating that this is not a “routine event”, otherwise more cases will be seen. A report published on the official website of the US magazine "Science" on the 24th quoted Columbia University virologist Angela Rasmussen as saying that this secondary infection patient may be a rare case of not having a good immune response in the first infection. "I don't think this has a big impact on vaccines and immunity."

Scientists have also observed secondary infections in studies of other coronaviruses. The above report quoted Charlotte Holdcroft, a virologist at the University of Cambridge, as saying that tests conducted in the United Kingdom in the 1980s showed that some people can be artificially infected one year after being infected with the coronavirus that causes the common cold. Infect again. Holdcroft said that most virologists expect a similar situation to occur in the new crown virus infection, which is more a question of how often it occurs than whether it occurs. The British trial also showed that participants who had a weak immune response during the first infection were more likely to be infected again.

Gu Alie, deputy dean of the Suriford School of Public Health of the National University of Singapore, told the media that it is not clear how common the re-infection of new crown patients is, but it is certain that re-infection within 6 months is very rare. It is known that the human body’s immunity to other respiratory viruses will weaken over time, such as influenza. Therefore, it is recommended that high-risk groups be vaccinated every year.

There are also scientific researchers who have seen a positive side from the secondary infection cases. According to the researchers, the patient was asymptomatic during the second infection. Oregon Health and Science University Viral Immunologist Mark Slivka told Science magazine that this shows that even if the patient is infected with a different strain than the first time, he is protected by the immune system.

Akiko Iwasaki, professor of immunology at Yale University, commented on social media: "(This patient) the secondary infection is asymptomatic, indicating that although the immune system is not capable of resisting re-infection, it still protects the body from disease. Iwasaki also emphasized that because of the existence of secondary infection, it is unlikely that the so-called “herd immunity” can be eliminated through natural infection. The only safe and effective way to achieve herd immunity is vaccination.