Because the virus will replicate the genetic genome in the process of transmission, due to its inevitable replication errors, the virus genome changes, resulting in mutant strains, which brings new challenges to epidemic prevention. However, not all mutations will bring great risks. Only some mutations will change the characteristics of the virus and enhance the infectivity and toxicity of the virus. Which mutant strains deserve attention? How infectious are they? What is the scope of dissemination? Does the existing vaccine have protective effect on it?
At present, the variant strains that pose the greatest threat to the world include alpha, beta, gamma and delta.
It spreads rapidly by the end of 2020 and becomes the mainstream mutant strain in the first half of 2021. In November 2020, the alpha variant was first detected in a sample in Kent, UK, in September. Alpha is particularly contagious. At the same time, cases infected with alpha have a stronger reaction. The patient coughs continuously, and mucus with virus will flow out of his mouth and nose – which also makes the virus more infectious.
AstraZeneca and Kexing vaccines are effective against alpha. According to the report on July 7 on the website of pharmaceutical times, the Canadian Institute of immunology found that the effectiveness of AstraZeneca vaccine on alpha was up to 90%; According to the Thai News Network on June 29, the Thai public health department found that the effectiveness of two doses of Kexing vaccine on alpha was 71% to 91%.
It has strong infectivity and strong immune escape ability. Beta was first found in the samples of South Africa in May 2020, and soon became the most widely spread virus variant in South Africa. At present, beta related cases have been found in 130 countries around the world. Beta is highly infectious and good at avoiding the tracking of the human immune system. The infection rate of Beta is about 50% higher than that of the original COVID-19, and the hospitalization rate, ICU occupancy rate and death risk are all higher. Pfizer vaccine has good resistance to beta. According to the BBC, the research data of Pfizer vaccine in Qatar show that its effectiveness in beta is 97%, especially in the protection of severe cases.
The Gamma variant strain is the biggest threat to the epidemic in South America. It was first discovered in the samples of Brazil in November 2020. It accounted for 76% of the new crown cases in South America in June 2021. It is the most important COVID-19 strain in South America, and has spread to 75 countries including the United States, Britain and Russia. Gamma variant strain is highly infectious, which may increase the transmissibility by 1.4 ~ 2.2 times, and may lead to reinfection. However, the effectiveness of the vaccine on gamma is still high.
Of course, people pay special attention to the popular mutant strain (delta strain) in India. Sars-cov-2 b.1.617.2 (delta) mutant was first discovered in Maharashtra, India at the end of 2020, and spread all over India. Its epidemic speed is much faster than the previously existing b.1.617.1 (kappa) and b.1.1.7 (alpha) pedigrees. At present, it has spread to more than 90 countries around the world. Delta strain not only caused the rapid spread of local cases in Guangzhou and other places in China, but also landed in the UK and was detected since March this year.
According to the global shared influenza data initiative (gisaid), as of July 26, delta accounted for 84% of infected cases in Asia, 97% in the UK and 80% in the world. The World Health Organization and the European Center for Disease Control and prevention jointly issued an epidemic report 23. According to the current trend, the delta strain will become the world’s leading COVID-19 mutant in the next few months. Unless there are more competitive strains, the delta strain will continue to spread and replace other variant strains. Delta is more infectious than any new crown variant strain in the past, but there is no detailed data on whether it will lead to more serious diseases.
Delta is 50% more infectious than Alpha and two times as old as COVID-19. Why does delta virus strain have such strong transmission power? Recently, Professor Ravi Gupta of University of Cambridge and his team found that Delta new crown virus can cause super strong transmission by evading neutralizing antibody and increasing replication ability. Its research results were published in Nature, an international famous journal in September 6, 2021.
In an analysis of more than 130 vaccinated COVID-19 infected patients in three centers in India, it was observed that the effectiveness of AstraZeneca vaccine on B.1.617.2 was lower than that of non B.1.617.2 virus, which reconfirmed the results of in vitro studies, that is, the sensitivity of SARS-CoV-2 B.1.617.2 (Delta) to neutralizing antibodies decreased and the replication fitness increased. It results in immune evasion and higher infectivity of the virus. Therefore, in view of the weakening of vaccine efficacy of highly evolved and immune evasive b.1.617.2 (delta) variant, it reminds us again that strict sensing and control measures still need to be taken in the post vaccination era.
How should vaccines change?
The greatest achievement of global anti epidemic is the listing of new crown vaccine by the end of 2020. It is not only the inactivated vaccine and recombinant subunit vaccine prepared with existing technology, but also the mRNA vaccine and adenovirus vector vaccine applied for the first time. Vaccine is an important means to control the epidemic. After the start of COVID-19, the development of various vaccines has been a great achievement.
However, having a vaccine does not mean that the epidemic can be controlled. The first key point is to put one or more needles in the arms of more than 70% of people around the world. In human history, it has never been done in a few years. As of September 14, the proportion of people who have completed vaccination in the world has just exceeded 30%, which is far from the goal of 70%. Less than 20 countries have vaccination rates of more than 70%.
In less than 10 months, the vaccine was completed at more than 2 billion 300 million, but hitherto unknown, it is too slow for COVID-19 to control. It is one of the reasons for this epidemic caused by delta strain that there is not enough mass immunity.
Large scale vaccination has caused evolutionary pressure on COVID-19. Due to the lack of inoculation rate, sufficient time variation of the virus is given, resulting in the emergence of new mutant strains and the ability to escape immunity. In the near future, there may be variation strains that can escape vaccine.
Another key point of vaccine control of COVID-19 is that it can cope with the variation of the virus. The vaccine is still at a constant state relative to the change of the virus. The previous generation of vaccines is based on beta and has not yet been listed. The prevention ability of delta strain decreased in varying degrees. Whether in terms of vaccination scale or renewal, the vaccine lags behind the virus by more than one step.
Fortunately, however, vaccinators can indirectly protect those who are not vaccinated, especially the elderly and children with low vaccination rate. The research of Israel Institute of technology has confirmed that vaccination can effectively protect the unvaccinated population. After monitoring 177 communities and analyzing the incidence of new crown infection among all unvaccinated people under the age of 16, the positive rate of unvaccinated people will drop twice for every 20% of the population. These data tell us that effective vaccination can not only improve individual resistance to the virus, but also help to improve the resistance of the whole population to the virus and significantly slow down the spread of the virus.
At present, only by completing the extensive vaccination of the vaccine can we establish a barrier to the spread of the virus. Once there is a virus input, even the mutated virus, its transmission speed will be greatly reduced. At this time, we can calmly and calmly take accurate prevention and control, greatly reduce the risk level of the virus and maintain the normal opening and operation of the world.
Epidemic situation and us
COVID-19 will definitely continue for a period of time. There is no accurate way to say how long it will last. Some experts believe that if we insist on vaccination, the epidemic situation is expected to be controlled in 2022, while others predict that more vicious variants will appear in 2022 and the epidemic will last longer. This is a difficult problem for governments. At present, a few countries that are capable of epidemic prevention adopt the strategy of clearing, a few adopt the strategy of lying flat, and most take the middle route.
More and more countries lie flat, but it is based on the premise of full opening after the vaccination rate reaches 70-80%. Most countries are taking control measures to varying degrees, that is, the lives of most people in the world are still affected by the epidemic. What kind of epidemic prevention strategy to adopt depends on many factors such as national conditions, social forms and people’s recognition. It is not comparable with each other. The strategy suitable for the situation of our country is the best strategy. For ordinary people, it is not this point that should be considered, but how to spend the disaster safely.
First, vaccinate. No matter what kind of vaccine, its effectiveness in preventing infection is affected by virus variation, but it still has very high effectiveness in preventing severe illness and death, so vaccination is undoubtedly the first choice.
Secondly, eliminate your own risk factors as much as possible. Everyone is not equal in front of the new crown. The risk of severe illness and death of the elderly and those with basic diseases is much higher than that of other groups. Old age is inevitable. Basic diseases cannot be cured, but can be well controlled. Therefore, we should more actively control relevant indicators and symptoms.
Among various risk factors, obesity is the number one risk and can be reversed. This risk factor can be completely eliminated through weight loss. Therefore, overweight people must strive to reduce their weight to a normal level and control the strain.
Diabetes and hypertension are two other major risks, but if blood sugar and blood pressure are controlled, they will not be considered as high-risk groups. Blood glucose and blood pressure should be controlled within normal limits through improvement of lifestyle and medication. Heart disease is also a major risk factor. We should control blood lipids and blood pressure, eat a healthy diet and exercise more to reduce the risk of cardiovascular disease.
Finally, adjust your mental state. During the epidemic, global anxiety, many people even to the degree of depression. We should constantly adjust our mentality and take various measures to relax ourselves in order to cope with the great pressure brought by the epidemic. The epidemic will eventually pass. Don’t let the epidemic make physical and mental scars.