Views: 0 Author: Site Editor Publish Time: 2022-07-20 Origin: Site
Currently, the New Coronavirus epidemic is still spreading globally, and the Omicron mutant strains BA.4 and BA.5 are becoming the main epidemic strains worldwide. Recently, there is an epidemic in some places in China, and the BA.4 and BA.5 mutant strains from outside China were found by sequencing the viral genes of infected patients. What is the transmissibility and pathogenicity of BA.4 and BA.5 mutant strains? Is the existing vaccine for the new coronavirus effective? Can our current prevention and control measures cope with them?
No significant change in pathogenicity, still a major threat to elderly and underlying patient population
"Compared with previous mutant strains, the BA.4 and BA.5 mutant strains are significantly more transmissible." Dong Xiaoping, chief virologist at the CDC, introduced that, first, the incubation period is significantly shorter, meaning that it can cause infected people to appear positive in a shorter period of time, with a stronger ability to spread the virus outward. Secondly, studies in countries and regions such as Japan and South Africa have shown that the transmission coefficient R0 value reaches 18 with a high rate of transmission without interference or with little intervention of public health measures. In addition, in some European countries as well as in the United States, the BA.5 variant has replaced other branches of the Omicron variant as the dominant strain. Image from the Internet
According to Dong Xiaoping, the viral transmission coefficient R0 is only an initial speed of virus transmission. For BA.4 and BA.5 variant strains, strong public health measures, vaccination, etc., can bring down the very high R0 value rapidly.
"Compared with other mutant strains of Omicron, BA.4 and BA.5 mutant strains are not significantly more and less pathogenic." Dong said that their clinical consequences were essentially equal from the available study data. "The BA.4 and BA.5 variant strains appear to be massively infected and remain fatal for older people with underlying disease. So we don't need to overemphasize how powerful they are, and we can't take them too lightly."
Existing vaccines effective in preventing serious illness and death
BA.4 and BA.5 are offshoots of the Omicron variant, which has the exact same key region S protein and is still essentially the Omicron variant, Dong said. At present, there is no complete data to verify whether the protection rate of our vaccine against BA.4 and BA.5 variant strains has changed. From some limited data reported internationally, virus variation can have some effect on the effectiveness of the vaccine. The effect was mainly seen through in vitro experiments, i.e., the neutralization experiments with BA.4 and BA.5 variants using sera after vaccination, and it was found that the inhibition effect was indeed reduced. However, there is no data to prove the overall protective effect of the vaccine.
The vaccine protection effect is divided into three levels: the first one is the protection effect on death and critical illness, the second one is the protection effect on hospitalization or overt infection, and the third one is the effect on infection or transmission power. Dong Xiaoping introduced that the research data in China and international research data show that inactivated vaccine, adenovirus vector vaccine, mRNA vaccine, etc. have good effect against death and critical illness and also obvious effect against hospitalization for Omicron variant strains BA.1 and BA.2. BA.4 and BA.5 variant strains have no essential changes, so the existing vaccines are still effective against death, critical illness and The existing vaccines are still effective in preventing death, critical illness and hospitalization. Of course, the effectiveness of the vaccine in preventing infection with the BA.4 and BA.5 variants remains to be seen in larger data. "Therefore, those who have not completed their booster immunization are advised to get vaccinated as soon as possible."
"Immune escape is not a very uncommon thing." Dong Xiaoping said the reason why the new coronavirus has to keep mutating is because it has to find a way out of the existing immune barrier. for the BA.4 and BA.5 variants to become a dominant strain, they have to produce some immune escape. Immune escape is not terrible, it depends on the effectiveness of the existing vaccines. At present, a large number of studies have shown that the immune protection effect still exists regardless of the original strain or the current strain, it is just a matter of high and low.
Prevention and control measures and prevention and control programs have not changed fundamentally
"China's prevention and control measures and prevention and control programs have not changed fundamentally." Dong Xiaoping said that virus mutations are common, and only when the mutations are very strong will they affect public health measures. China's existing prevention and control measures are effective against both BA.4 and BA.5 mutant strains. They have variation, but not enough to affect the need to readjust our public health measures and prevention and control programs.
In the ninth edition of the prevention and control program, China has brought the monitoring of the new coronavirus to a higher position. Dong Xiaoping introduced, the original viral disease prevention and control are from the infected, while the frontier of prevention and control of the new coronavirus has moved to the normal population. Nucleic acid testing is a very important measure. In the program, the proposed hierarchical testing and nucleic acid screening program, such as the monitoring of high-risk occupational groups once a day nucleic acid testing, etc., can be timely detection of infected people to prevent the spread of the epidemic.
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In the ninth edition of the prevention and control program to the entry of people in the quarantine period of adjustment in line with the actual. Dong Xiaoping analyzed that China changed the isolation period from "14+7" to "7+3", referring to the situation in many international countries, and through research and analysis of domestic epidemic data, it was found that the 7-day isolation was very effective, because the vast majority of people will be positive within 7 days. day positivity occurs. This adjustment can be applied to BA.1 and BA.2 variants, and equally to BA.4 and BA.5 variants.
"We should not take the BA.4 and BA.5 variants lightly. If left unattended, once the infection is extended to the elderly population and to those with underlying diseases, it can also cause terrible results." Dong Xiaoping said, we should adhere to the general strategy of "external prevention of importation and internal prevention of rebound" and the general policy of "dynamic clearance", so as to control the impact of the epidemic in the nascent state.
