Relatively "mild" Olmikeron

In Chennai, India, medical staff work in a COVID-19 ward. As of the evening of December 30, 2021 local time, there were more than 1,160 cases of infection with the Omiljun strain in India. One of the people infected with the Omikejong strain from Maharashtra died, the first case of death from the Omiljun strain in India. (Visual China/Photo)

After entering 2022, Aumechon has replaced Delta as the most popular strain in the world with its stronger infectivity and immune escape ability. According to GISAID, the world's largest COVID-19 epidemic data sharing platform, of the more than 430,000 COVID-19 gene sequences from mid-February to mid-March, the sequence of the Omiljunn variant is close to 430,000, accounting for 99.9%, and Delta has only 400, accounting for less than 0.1%. As early as the time of Omilon's discovery, epidemiologists in South Africa initially observed in clinical data that the symptoms caused by the new variant after infecting people seemed to be milder than during the Delta epidemic. But is it light? How much lighter? Is it because the virus itself is significantly less toxic, or is it because of the group-level protection effect produced by more people vaccinating?

These questions have been lacking in larger epidemiological scientific data to analyze the answers. However, answering these questions can help better assess the impact of the Opichron variant on the COVID-19 pandemic and provide a basis for adjustments to epidemic prevention policies. On March 16, 2022, scientists from the University of Cambridge, Imperial College London, the UK Health Security Agency and other institutions used local epidemiological data to answer questions about the severity of symptoms after The Lancet, which has been published online. Through a clinical comparison of millions of infection cases, they confirmed that symptoms became significantly lighter after infection with Omicron compared to the effects of Delta on people.

69% lower risk of death

From the most concerned death and hospitalization data, the risk of hospitalization and death caused by Omiljung infection is only 0.41 and 0.31 at the time of Delta infection, which is equivalent to reducing the risk of hospitalization by 59%, reducing the risk of death by 69%, and even reducing the risk of going to the hospital by 44% in the case of local infection on-demand hospitalization. Judging from these indicators that indirectly reflect the symptoms of the new crown, although the risk is generally reduced, the risk reduction varies by age group, and in general, the risk of hospitalization has decreased significantly among people over 20 years old.

Scientists have previously found that after contracting the new crown, age is an important risk factor, and the older the elderly, the higher the risk of hospitalization and severe illness. The latest research has found that compared with the consequences of infecting Delta, the risk of hospitalization for people over 50 years old after infection with Omikeron has decreased by between 50% and 75%, the risk of 50- and 60-year-olds has dropped more significantly, and the risk of hospitalization can be reduced by 75% for people in their 60s. For people over 80, this age group was originally at higher risk, but the risk drop was slightly lower, at 53 percent, meaning that in most cases, after Opmikron replaced Delta, the risk of hospitalization for the most at-risk elderly was also halved.

The risk of going to the hospital and the risk reduction of infection and death are similar to those of hospitalization, with people over 80 years of age having less risk and still facing the greatest risk of death from COVID-19. The difference is that deaths among young people due to COVID-19 are extremely rare, so there is a lack of sufficient data to estimate changes in the risk of death for people under the age of 30. Deaths from COVID-10 are also rare, but after splitting the overall risk of this group of people with large differences in physical status, the researchers found that infants under 1 year of age had a higher risk than those aged 1 to 4 and 5 to 9 years, but these differences were not significant enough.

In fact, in terms of overall risk, including hospitalization and hospital visits, children under the age of 10, after the Omiljung epidemic, were different from other groups, with insignificant declines and similar to those at Delta. For hospitalization risk, there is even a 10% increase. The risk of hospitalization for people aged 10 to 19 has decreased, but only 17%. Why is the risk reduction in children under 10 years of age after infection with Omicron not significant? The researchers analyzed that it may be related to the clinical symptoms and admission criteria of Omicron. In February 2022, Nature published several studies showing that Omilon was more likely to replicate in the upper respiratory tract than in the lungs. On the one hand, this may explain the reason for the reduction of severe COVID-19, on the other hand, it also means that children are more likely to have some upper respiratory symptoms and fever. As far as the local COVID-19 treatment policy is concerned, adults with milder symptoms generally do not stay in hospital or even go to the hospital. But relatively speaking, young children, especially those under the age of 10, once they are sick, parents and doctors will pay more attention to it, and the admission standard will be lowered. Statistics on those under 10 years of age infected with Omeikron show that the younger the age after infection, the more likely they are to be hospitalized, while the proportion of hospitalizations under 1 year of age is the highest.

Both the virus has decreased in its virulence and vaccine effectiveness

These important figures are based on more than 1.5 million local COVID-19 infections in England. From November 29, 2021 to January 9, 2022, more than 4 million cases of infection were found locally, of which more than 1.5 million were accompanied by information such as the type of mutant strain, which provided the conditions for researchers to compare the symptoms of Omi kerong and Delta through large-scale data. Delta was the dominant local strain from May to December 2021, and since the end of November, the first case of Omilon infection has been reported locally, and the number of confirmed cases of Omilon has begun to increase, and by January 10, 2022, the proportion of gene sequencing cases has exceeded 99%. As a result, more than 1 million people infected with Omikejong were included in the latest study, and nearly 450,000 were Indah cases.

In terms of post-infection risk, using existing records, the researchers focused on three outcomes: hospitalization, hospital visits, and death. Among them, the new crown hospitalization refers to the hospitalization within 14 days after the test is positive, and the time limit of going to the hospital is also within 14 days after the test is positive, of course, the actual situation of going to the hospital may be more complicated, hospitalization, emergency or accident may be possible. The statistical period of COVID-19 deaths is longer, and those who die within 28 days after a positive test are defined as COVID-19 deaths and are included in the study. Moreover, the vaccination rate of the elderly in England is very high, and as of January 9, 2022, more than 90% of the elderly over 70 years old have received a third injection, and the proportion of people who have had at least one injection has exceeded 95%. Among younger people, the rate of booster injection vaccination is lower, and only 43% of those aged 30 to 34 years. These vaccination data, combined with infections, allowed the researchers to assess what role the vaccine played in people infected with Omikerong.

The results found that compared with those who had not been vaccinated, the risk of hospitalization and death was greatly reduced. But this risk is relatively low when dealing with Delta, indicating that vaccines have a greater effect when dealing with Delta, while vaccines are slightly less protective when confronted with Opicron. This is similar to the conclusion of higher breakthrough infections found in many of the Ami kerong studies. In turn, it also shows that the overall risk of hospitalization and death in Omi kerong observed so far is largely due to the weakening of the toxicity of the virus itself, and because the protective effect of the vaccine is also reduced, offsetting part of the risk reduction. In terms of the reduction in the risk of hospitalization, while the overall risk of hospitalization after the Omikejong epidemic was reduced by 59%, the risk was reduced by 70% for those who did not receive the vaccine.

In addition, previous infection experiences are useful in reducing the risk of death, whether vaccinated or not. For people who have not been vaccinated, this natural infection experience can also play a significant protective role in preventing hospitalization of covid-19, etc., reducing the risk by nearly half compared to people who have not experienced infection. If vaccinated, previous experiences of COVID-19 will not provide additional protection in preventing hospitalization. Although the protective effect of the vaccine is weakened in the face of Omilon, after the intensive injection, the overall risk of hospitalization can be reduced by more than 70% compared with those who have not been given. It should be noted that the protective effect of different vaccines is different, and the latest study only involves three locally used vaccines, namely the mRNA vaccine BNT162b2 developed by Pfizer and other companies, the mRNA-1273 of Modena, and the vaccine ChAdOx1 jointly developed by Oxford University and AstraZeneca. The study once again confirmed that the effect of the AstraZeneca vaccine was not as good as the mRNA vaccine of Pfizer, Modena and other companies, and the protective effect on preventing hospitalization after infection with the new crown was the greatest, and the protective effect was better if the mRNA vaccine was given a booster injection.

Re-infection is markedly increased

In addition to being highly contagious and milder in symptoms, which have been confirmed in the latest studies, The Enhanced Risk of Re-infection with COVID-19 has also been confirmed. At the end of 2021, when Omi kerong was first discovered by scientists, the epidemiological data showed that many people were re-infected, that is, they were infected with different types of new coronavirus mutant strains. Large-scale data from the UK shows that of the nearly 450,000 Delta cases, nearly 6,000 people, or 1.3%, were re-infected. Among the more than 1 million people infected with Omikerong, more than 10,000 people were re-infected, accounting for 9.6%. Re-infection here refers to the situation where the interval between the two confirmed infections is more than 90 days, indicating that they are two independent covid-19 infection events.

While The symptoms of COVID-19 infection have become significantly lighter in Aumechjong, the increase in re-infection has added new uncertainty to the prevention and control of the epidemic. In February 2022, scientists in Denmark, Qatar and other places also found that people could even infect Omiljung twice in the rapidly spreading epidemic. It mainly refers to the phenomenon of continuous infection with Omi kerong subtypes BA.1 and BA.2. When Omikron first appeared, the most widely spread was BA.1, which spread rapidly. After analyzing the relationship between the two infections, researchers in Qatar believe that the infection of either of the two main subtypes of Omi kerong has a strong protective effect on preventing infection with the other, but this protection is not absolute. The protection rate against BA.2 is estimated to be 94.9% if ba.1 is first infected, and 85.6% against BA.1 if ba.2 is infected first. The study was published on the preprint website medRxiv on February 25, 2022, and has not yet been peer-reviewed.

After the emergence of Omilon, based on the local situation, the UK government has announced that all COVID-19-related travel restrictions will be lifted from 18 March 2022, which means that anyone entering the UK will no longer even need to do a nucleic acid test. However, the notice also pointed out that this completely liberalized epidemic prevention policy may still be urgently adjusted with the situation of the new crown strain in the future. However, the epidemic situation and epidemic prevention goals vary from country to country, so in the face of the latest changes in Aumicron, it is still necessary to adjust according to its own situation.

On March 14, the National Health Commission and other institutions launched the "Diagnosis and Treatment Plan for Novel Coronavirus Pneumonia (Trial Ninth Edition)" in response to the new characteristics of the clinical manifestations of Aomi Kerong patients and the listing of therapeutic drugs, which includes the implementation of centralized isolation and management of mild cases, and if the condition worsens, they are transferred to designated hospitals for treatment. On March 18, at the press conference of the State Council Information Office, the relevant person in charge pointed out that the dynamic zeroing policy is still the current epidemic prevention line that must be guarded, and the revision of the ninth edition of the diagnosis and treatment plan does not mean that the prevention and control policy is relaxed.

As researchers from cambridge and other institutions in the latest study have highlighted, although they did find that people with more toxic symptoms after infection with Omiclon than Delta, a more toxic variant, does not mean that the new crown has evolved in a less toxic direction since then. In fact, from the original strain of COVID-19 to Alpha to Delta, symptoms are worse after infection. What's more, although the virulence of Omi kerong has weakened, the infectivity and ability to break through immunity are stronger, and it is still necessary to continue to pay attention to the mutation of the virus and the trend of the epidemic in the future.

Southern Weekend reporter Wang Jiangtao