Has the harm of Aomi Kerong been greatly reduced?

On December 14, 2021, the first positive case of the new crown "Omiljung" strain appeared in Guangzhou, and a citizen walked through a poster of a battle "epidemic" in the gold mining community. (Southern Weekend reporter Weng Huan/photo)

Since the end of 2021, the new coronavirus variant, Olmiqueron, has received special attention around the world, and the variant has rapidly replaced Delta as the most popular strain in many places. On GISAID, the world's largest COVID-19 gene sequence sharing platform, more than 98 percent of the more than 400,000 sample sequences uploaded in the month before February 11, 2022, and Delta accounted for more than 98 percent.

As early as when Omiqueron was first discovered by scientists, researchers analyzed epidemiological survey data and clinical treatment data and believed that Compared with Delta, Omilon's infectivity and immune escape ability are likely to be stronger, but the symptoms after infection will be lighter than those of Delta. This information has also led some places to consider whether the overall harm of the COVID-19 pandemic to society will be significantly reduced.

However, a recent comparative study of clinical data found that the symptoms did not significantly lighten after infection with Omicron excluding the effects of vaccines.

Just slightly lighter than Delta

Researchers at Cydasnay Medical Center in Los Angeles compared the situation of more than a thousand COVID-19 inpatients using clinical data from hospital electronic records, including more than 300 hospitalized between July and September 2021, when Delta was the dominant local epidemic strain and more than 700 were admitted from December 2021 to January 2022, when Omilon was the dominant local strain. Compared with previous clinical studies of Omi kerong, this comparative study especially considers the impact of vaccines, and divides patients into unvaccinated people and those who are fully vaccinated at each time period, which is convenient for observing the symptoms of Omilon and Delta infected people in different vaccine states.

Statistics found that the proportion of ICU for severe illness in the Delta stage was 23.3%, and 13.6% received invasive mechanical ventilation therapy, while the two indicators at the Omi kerong stage, which were 16.8% and 9.2%, respectively, looked significantly lower, but when the patients were distinguished according to whether they were vaccinated, the two indicators were still lower, but the difference between entering the ICU and receiving mechanical ventilation therapy in the two stages was not statistically significant. Suggesting that the milder symptoms observed during the more prevalence phase of Omikejong may be largely driven by immune protection formed by vaccination at the population-wide level, rather than because the virus itself is significantly less toxic. The study was published in February 2022 in the Weekly Journal of Morbidity and Mortality (MMWR).

For mortality indicators, the Omicron phase has dropped significantly. Compared with the 10.6% hospitalization mortality rate of patients in the Delta stage (after the local infection with the new crown, the general severe disease will only be hospitalized), the mortality rate of fully vaccinated people after hospitalization with Omi kerong infection is only 3.4%. Vaccine protection against patients in Omilton is also reflected in the proportion of people who enter the ICU, which is less likely to be admitted to the ICU after vaccination, especially for those who have also received booster injections.

But as the epidemic changes, the effect of vaccines is not static. While the researchers did not disclose in detail the types of vaccines administered in the hospitalized samples, local statistics show that from mid-July to mid-December 2021, the proportion of local full vaccinations has increased from nearly 65% to 77%, an increase of less than 20%, but among these people, the proportion of COVID-19 hospitalizations has increased from 25% to 40%, an increase of 60%. The researchers estimate that this reflects, on the one hand, that the vaccine's immunity weakens over time, and that on the other hand, it may also be due to the increased resistance of Thermolurgon to vaccine-neutralizing antibodies.

These latest clinical analyses show that although the overall symptom severity after the Omilton epidemic was reduced compared to that of the Delta epidemic, it was not particularly significant, and it is still a new coronavirus strain that can cause severe illness and even death. Moreover, a large number of studies have found that Aomi Kerong is also significantly more contagious and immune to escape than Delta, which means that the ability of the epidemic to spread and the overall harm caused by the epidemic may be greater and therefore cannot be ignored.

Stronger BA.2 subtype

What's more, Amikeron is still mutating. Since the Greek alphabet was named by B.1.1.529 at the end of November 2021, a variety of subtypes such as BA.1, BA.1.1, BA.2, and BA.3 have been identified in the Sequence of the Semikron strain. In the early days, Omirkron was dominated by BA.1, and now, in some countries, BA.2 is increasing rapidly. At one point in the GISAID sequence in early February, it reached one-fifth. The World Health Organization also recommends a special study of the characteristics of the BA.2 subtype when tracking the new crown variant.

Researchers at the University of Tokyo's Institute of Medicine and other institutions recently compared the transmission characteristics of BA.2 and BA.1 and concluded that the potential risks of BA.2 to global health may be higher. To confirm whether BA.2 is more contagious, the researchers did a series of comparative studies. Modeling and analysis of the epidemic data estimates that the effective regeneration of BA.2 is on average 1.4 times higher than that of BA.1, which means that BA.2 spreads more easily in the population. In the neutralization experiment, BA.2 not only has a strong resistance to a variety of vaccine-induced antiserum, monoclonal antibodies and rehabilitation serums for the treatment of new crown, but also reflects similar immune resistance to BA.1, and in hamster rehabilitation serum neutralization experiments, BA.2 also has significantly higher resistance to rehabilitation serum produced after infection with BA.1. This suggests that immunity gained by infecting the BA.1 Semikron variant may not be as effective against BA.2. Experiments on hamster virus infection also found that BA.2 was more pathogenic than BA.1 and spread more efficiently in the lungs. The study was published on the preprint website bioRxiv on February 15, 2022 and has not yet been peer-reviewed.

Although hamsters are not human, in the January 2022 Epidemic in Hong Kong, it has been confirmed that a number of "rat-to-human" transmission chains have been opened. Researchers at the University of Hong Kong, after investigating a pet store Delta outbreak, believe that hamsters can not only naturally infect the new crown in the real world, but also achieve "rat-to-mouse" and "rat-to-human". Hamster virus experiments provide some evidence to understand the infectious characteristics of the Aomi Kerong BA.2 subtype, and more accurate characteristics of the virus still need to be discovered based on human observations and experiments. In view of the obvious differences in the genetic sequences of BA.2 and BA.1, and the worrying characteristics shown in the available data, researchers at the University of Tokyo and other institutions also suggested that BA.2 be assigned a greek alphabet code to be independent of the many subtypes of Omikron for more in-depth monitoring.

At present, there are many data on the high infectivity of BA.2, but there is still insufficient evidence on the severity of symptoms after infection with BA.2. Considering that the infectivity of the Omilon BA.2 epidemic has reached a new high, even if the symptoms of the Omilon infection have decreased compared with Those of Delta, there is still uncertainty about how the overall harm of the new crown pneumonia epidemic to global health will change after the significant increase in the number of infected people.

Southern Weekend reporter Wang Jiangtao