Recently, the epidemic situation in many parts of the mainland has rebounded, and 14 provinces have reported confirmed cases of Omicron. At the same time, some self-media believe that "the symptoms of Omi kerong are milder, equivalent to a large flu".
Compared with other strains, how virulent is Aomi Kerong, is it really a "big flu"?
Real-world data from South Africa and the United States show that compared with Delta, hospitalization rates for those infected in Aumicroon have been reduced by 40%-67%, and the mortality rate of hospitalized patients has been reduced by 83%-91%. As a result, the researchers came to the conclusion that the Olmikeron variant was milder than Delta, and the paper was published in JAMA and medRxiv, respectively.
Image source: JAMA
(Details of the content of the poke: Omikejong infected people to Delta immunity increased by 4.4 times; the rebound of the epidemic in many places in the mainland, how to prevent the import of external defense?) ）
However, in the above study, 24.2% to 49.9% of the infected people had been vaccinated, and the severity of the disease was affected by the vaccination situation, making it difficult to visually compare the true virulence of Omilon and Delta. Conversely, in the case of unvaccinated, it is more intuitive to compare the severity of the disease caused by the two strains.
On January 13, the study published in medRxiv by Case Western Reserve University and the National Institutes of Health compared the severity of the disease after the first infection of the new crown virus in the United States after the Omicron epidemic (unvaccinated) under 5 years of age. It was the world's first study to exclude the confounding factor of vaccination and simply compare the toxicity of Omilon with Delta.
Image source: medRxiv
The retrospective cohort study included a total of 79,592 children under 5 years of age who were first infected with COVID-19 and divided them into 3 groups:
(1) The Omikejong group = 7,201 people
First infection with COVID-19 between 26 December 2021 and 6 January 2022. During those two weeks, Omi kerong accounted for more than 92 percent of all circulating virus variants in the United States, according to CDC data.
(2) Delta group = 63,203 people
First infection with COVID-19 between 1 September 2021 and 15 November 2021. During this period, Delta was the main strain, accounting for 99.0%.
(3) Delta Group 2 = 9,188 people
First infection with COVID-19 between 16 November 2021 and 30 November 2021. This was before the Omicron variant was detected in the United States, but Delta remained dominant.
Comparing the baseline characteristics of the patients, the infected people in the Semikron group were 0.24 years younger than the age of Delta (The Omikeron group: Delta group = 1.49 years± 1.42 years: 1.73 ± 1.41 years). Comparing races, it was found that Aumechon preferred black people, while Delta preferred white people, but had no preference among Asian races. Compared with Delta, Omicron causes fewer comorbidities, such as cancer, asthma, obesity, etc.
In order to reach more scientifically rigorous conclusions, the researchers used the tendency score matching method to adjust the data, eliminating the differences caused by confounding factors between the Omikeron and Delta groups.
To compare the differences in disease severity caused by the two strains, the researchers included the number of emergency department visits, hospitalizations, ICUs, and mechanical ventilation aids "within a three-day window after first infection with COVID-19" as criteria.
The results showed that compared with the Delta group, the number of emergency department visits in the Omiqueron group decreased by 29% (Omilon group: Delta group = 18.83%: 26.67%), the number of hospitalizations decreased by 67% (1.04% to 3.14%), the number of severe patients in ICU decreased by 68% (0.14% to 0.43%), and the use of mechanical ventilation assist was reduced by 71% (0.33% to 1.15%). It was proved that the severity of the disease in the Omicron group was significantly lower than that in the Delta group.
In addition, the researchers also compared the data from the two groups of Delta and found no significant difference in the severity of the disease between the two groups.
The disease situation suggesting that the infected person was not affected by a mixture of factors such as the time of infection, the cold weather, and whether there was a holiday, thus confirming that the difference between Omiqueron and Delta stemmed from the inherent characteristics of the virus itself.
As there were very few deaths among the children under investigation within 3 days of infection with the two strains, the risk of death was not included in this trial.
In summary, this study confirms that the severity of the condition of Omiljung infected people is less severe than that of Delta in the absence of vaccination, and the hospitalization rate of the former is only 1/3 of the latter.
But even with milder symptoms, among unvaccinated people, those infected with Omikerong still had a 1.04 percent hospitalization rate, a 0.14 percent severe illness rate, and a 0.33 percent mechanical ventilation rate.
At this stage, the coverage rate of the mainland population vaccinated against the new crown virus has reached 89.63%. Conversely, more than 10% of the population is still unvaccinated, and most of this population is not eligible for vaccination. Omiljung's strong immune escape ability makes it difficult for vaccinated people to escape infection, and although this part of the population is asymptomatic or mild, it can still be transmitted to unvaccinated people. Once the latter is infected, it will produce a higher rate of hospitalization and severe illness.
图源：Our world in data
That is to say, although infection with Omi kerong shows milder symptoms, it will still place a great burden on the medical industry due to its increased transmissibility. Therefore, Omi kerong is by no means a "big flu" and should be more cautious about new strains.
bibliography:
[1] Maslo C, Friedland R, Toubkin M, Laubscher A, Akaloo T, Kama B. Characteristics and Outcomes of Hospitalized Patients in South Africa During the COVID-19 Omicron Wave Compared With Previous Waves. JAMA. Published online December 30, 2021. doi:10.1001/jama.2021.24868
[2] COVID infection severity in children under 5 years old before and after Omicron emergence in the US. Lindsey Wang, Nathan A. Berger, David C. Kaelber, Pamela B. Davis, Nora D. Volkow, Rong Xu. medRxiv 2022.01.12.22269179; doi: https://doi.org/10.1101/2022.01.12.22269179
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