What about Omicron's apparent reduction in toxicity? How can we protect ourselves?

In an interview with CCTV news on December 5, Tong Zhaohui, an expert on critical respiratory diseases invited by the Joint prevention and control mechanism of The State Council and director of the Beijing Institute of Respiratory Diseases, said that international and domestic monitoring data have confirmed that the Omicron and its evolutionary branches are significantly weaker in pathogenicity and virulence than the original strain and Delta and other variants.

According to Tong Zhaohui, the proportion of severe illness and death caused by the Omicron is significantly lower than that of the original strain and the variant of concern, which is not only the characteristics of the Omicron, but also related to the improvement of the population's immunization level and the active prevention strategy adopted by the country. The Omicron is currently causing relatively low rates of pneumonia or severe or critical illness compared with the 2009 pandemic.

So what to make of Tong's claim that "Omicron variants and their clades are significantly less virulent", and the relatively low proportion of severe cases of Omicron compared with 2009 H1N1 flu? What problems should ordinary people pay attention to in this case?

Like all RNA viruses, SARS-CoV-2 is prone to mutate. Since 2019, the World Health Organization (WHO) has named a total of five variants of concern (VOC), among which Omicron is currently the only variant circulating globally, showing its rapidly increasing transmission ability. At the same time, related reports on the weakened virulence of Omicron variant are increasing. Therefore, how to correctly view and understand this phenomenon is the basis for CDC to formulate corresponding control strategies, and also helps the public to understand and support the disease control policy.

Mutation of the novel coronavirus is inevitable

Due to the lack of proofreading activity in the process of RNA virus replication, the virus genome will produce some mutations in each replication generation in the cell. Most of the mutations have little effect on the virus, but some of the mutations will cause changes in virus transmission, pathogenicity and immunogenicity.

Compared with the original strain, there were nearly 100 variations in the genome of the Omicron, including base deletion, insertion and point mutation, and more than 600 evolutionary branches and subbranches were formed in the process of transmission. The recent local epidemic in China was caused by the spread of BA.2 and BA.5 branches and their subbranches. The novel coronavirus will continue to mutate. Although some experts believe that the virus genome has entered a stable period, it is not excluded that new variants of concern will continue to appear in the future, especially the genetic recombination between different variants. The impact of new variants of concern on the global epidemic cannot be judged at present.

The Omicron variant is more transmissible

Since its discovery in November 2021, the Omicron has swept the world in just a few months, demonstrating its extraordinary ability to spread.

Using mathematical models, the Nankai University team estimated that the Omicron variant is 37.5 percent more transmisable than the Delta variant. In South Africa, the effective reproduction number of Omicron variant, that is, the number of second-generation cases generated by confirmed Omicron infected patients was 3.31 times that of Delta variant, indicating that Omicron has stronger transmission ability.

The study found that the infection incubation period of Omicron variant was significantly shortened, the transmission generation was accelerated, the transmission concealment and transmission efficiency were significantly enhanced, and the reinfection caused by immune escape made Omicron have significant transmission advantages compared with other variants.

The Omicron variant is less virulent

Early in the Omicron epidemic, South African researchers found that its clinical manifestations and consequences were significantly lower than those of the Delta variant. Subsequently, German national surveillance data showed that the hospitalization rate of Delta variant was three times that of Omicron. More and more studies and clinical data showed that the virulence of Omicron variant was significantly reduced, mainly in the proportion of severe disease and death was significantly lower than that of the original strain and other variants of concern. A surveillance data in China also showed that more than 90% of Omicron variant children infected with the clinical classification of mild.

Through in vitro studies and animal experiments, it was found that compared with the original strain and other concerned variants, the Omictron formed smaller plaques and weaker cell fusion ability after infecting human cells, and the virus replication ability was significantly weakened. In animal models, the Omicron  also showed significantly attenuated replication levels in the upper and lower respiratory tracts of infected animals, resulting in improved lung pathology and reduced pathogenicity.

In conclusion, as Omicron has become the only prevalent variant of concern in China, due to its high transmissibility and weak pathogenicity, epidemic prevention and control in China is facing new situations and new tasks. In addition, the characteristics of Omicron immune escape require special attention for the protection of pregnant women, children, the elderly and immunodeficient people. Therefore, the continuous monitoring of the genetic variation of the novel coronavirus, especially the Omicron, will provide important basic data for epidemic prevention and control, vaccine and drug development.

Attenuated toxicity, but still need to pay attention to protection

Omicron is significantly less virulent, so does that mean there's no need to worry about COVID-19? Of course not. Everyone should still pay attention to personal protection, should pay attention to the following points:

1. For now, the single most important measure of personal protection is getting vaccinated against COVID-19.

2. For the general population, it is necessary to wash hands frequently, wear masks when going out, often ventilate, and do not gather. Balanced nutrition, proper rest, reasonable exercise, maintain a good attitude.

3. Patients with chronic underlying diseases should adhere to medication according to the doctor's advice. People with chronic respiratory diseases should avoid going out in bad weather, such as when the temperature drops sharply.

4. If you have fever, sore throat, cough and other discomfort, do health monitoring. If severe high-risk people have persistent high fever and breathing difficulties, they should go to the hospital in time to avoid the aggravation of the disease.