April 14, 2024

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Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?

Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?


Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it? Anti-infection effectiveness of current COVID-19 vaccines is reduced, but it can still prevent severe illness and death. 


India has set a “new record”. Data from the Ministry of Health of India on June 10 showed that 6,148 COVID-19 pneumonia deaths were added in the previous 24 hours. This broke the highest number of deaths in a single day set by the United States on February 12 this year (5444 cases) in a single country.


Since the end of May, the current round of the epidemic in India has gradually dropped from its peak. At present, many places including the capital New Delhi and the financial center Mumbai have been unblocked to varying degrees. In this regard, the Indian media is “not optimistic.” “India is facing the dual threats of delayed vaccination and the spread of variant strains. It is recommended that the government carefully unblock it.” The Times of India said.


On June 4, the National Center for Disease Control of India and others published a study on the pre-print platform, claiming that the mutant strain Delta was the chief culprit in detonating this round of the epidemic in India.


“We have three findings: the mutant strain Delta is easier to spread, has a higher escape immunity rate and secondary infection risk, and is more likely to break through vaccine protection.” Anu, director of the Institute of Genomics and Integrative Biology, Indian Council of Science and Industry Research Ragh Agrawal told the Economic Times of India, “Look at New Delhi. The world needs strong public health measures to curb the spread of the mutant Delta.”


Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?Photo caption: The electronic display on the street warns that there are cases of COVID-19 infection in this area. /AFP


Why is mutant strain Delta so much concerned?


The mutant strain Delta caused an uproar in India and the United Kingdom.


The mutant strain was originally called B.1.617.2 and first appeared in India in October 2020. On June 1, 2021 local time, the World Health Organization (WHO) listed it as a “mutant strain of high concern”. The other two mutant strains of the same lineage as Delta, B.1.617.1 and B.1.617.3, were observed to have a low transmission rate, so they were included in the “mutant strains that need attention”.


“Delta has a higher public health risk and is an important reason for the sharp increase in the number of infections and deaths in India since April.” The ABC has repeatedly reported the outbreak in India. Its article on June 9 stated that in February and March of this year, the capital New Delhi seemed to “walk out” of the hot zone, with an average of only more than 100 newly diagnosed cases per day.


By April, the number of new infections in a single day in New Delhi increased to nearly 30,000. “India’s COVID-19 epidemic is out of control.” In April and May, the Indian media shouted desperately. The BBC quoted New Delhi TV as reporting that multiple bodies were floating in the Yamuna River in Uttar Pradesh, India. “Due to the high cost of cremation and people worry that cremation of the deceased will cause infection, a large number of the dead have been abandoned on the river bank.”


Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?Photo caption: Locals in India pointed out that the high cost of cremation led to the abandonment of the deceased from COVID-19 on the banks of the Yamuna River. /BBC

“Ignoring the social distancing policy, not wearing masks, and holding various large-scale gatherings have created conditions for the rapid spread of the virus. But it cannot explain why there are still a large number of people infected with the disease in areas with high incidence of infection in the past, such as New Delhi.” Michigan State, USA Mukherjee, a university epidemiologist and Indian scholar, told the ABC. The serum sample survey estimates that more than half of the population in New Delhi is positive for COVID-19 antibodies. This ratio has almost formed “herd immunity.”


“The answer or the mutant strain Delta.” said Rainer McIntyre, the head of the biosafety research project at the Kobe Institute in Australia. Compared with the first discovered COVID-19 virus strain, the mutant strain Alpha, which first appeared in the UK, has a higher transmission power. 50%-100%. And Delta’s transmission power is 50% higher than it. This means that the transmission power of Delta is 100%-150% higher than that of the original strain.


Anurag Agrawal told the Economic Times of India that his research team sequenced and analyzed samples collected in New Delhi from November 2020 to May 2021. The results showed that the detection rate of Delta increased from 5% in February to 10% in March, and reached 60% in April.


Simultaneously with the increase in the Delta detection rate is the local diagnosis rate. By the third week of April, the positive rate of COVID-19 in New Delhi exceeded 36%. That is, in every 3 samples, there is a positive case of COVID-19. “This is the first time that India has confirmed that this round of the epidemic is related to the mutant strain.” Anurag Agrawal said, “I don’t think India would have an outbreak of this scale if there were no mutant strains.”


Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?Picture description: From February 2021 to April 2021, the number of Delta infection cases increased rapidly. /The National Centre for Disease Control, Delhi and the CSIR Institute of Genomics and Integrative Biology


“In this round of the epidemic, each patient’s performance is different.” Mumbai otolaryngology surgeon Heita Mafatia told Bloomberg that some people sought medical treatment for hearing loss, neck swelling and tonsillitis, and then were diagnosed with COVID-19. She also saw in the hospital that the initial symptoms were stomach pain, nausea, vomiting, loss of appetite, and joint pain. A study conducted by the University of New South Wales in Australia in May this year stated that in the variant strain infections that first appeared in South Africa and Brazil, there was almost no evidence that the above clinical symptoms would be caused.


Mumbai doctor Ganesh Manudan said that some people with COVID-19 infections have microscopic blood clots. “In the past two months, I have treated 8 COVID-19 patients with thrombosis, two of whom needed amputation. In 2020, there have been three or four cases of this kind of situation. Now there is one case in a week, and there is no history of thrombosis.”


Infectious disease doctor Abdul Gaffer told Bloomberg that there is not enough evidence to support that the mutant strain Delta is more likely to cause severe illness or death. But Choita Basu, who runs a medical institution on the outskirts of New Delhi, disagrees.


“Previously, about 1 out of every 10 confirmed patients needed supplemental oxygen. Now, 1 out of every 2 people.” Choita Basu emphasized that India’s medical oxygen supply continues to be tight. If this continues, more people may die due to lack of oxygen.


Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?Photo caption: The mutant strain Delta is considered to be an important cause of this “catastrophic” epidemic in India. /Reuters


WHO data shows that in the past 6 months, Delta has spread to more than 60 countries around the world.


“There are signs that the UK is in the initial stage of the third wave of COVID-19 outbreaks.” The British “Daily Mail” reported that on June 10, there were 7,540 new infections in a single day in the UK, an increase of 74.1% from last week. During the same period, the number of hospitalizations in the UK increased by nearly 40%, and the number of deaths fell by 50%.


At the same time, there has been an “exponential increase” in cases of Delta infection. “Delta accounts for 91% of the strains detected in the UK and has become the main epidemic strain in the UK.” The Daily Mail quoted British Health Secretary Matt Hancock as saying that the UK was originally scheduled to “comprehensively resolve” on June 21. “Closed”, it may be delayed by 2-4 weeks due to the widespread spread of Delta.


Picture from The Daily Mail


“Delta accounts for more than 6% of virus sequencing in the United States. In some states in the western United States, the detection rate may reach 18%. The actual number of infections may be higher.” On June 8, local time, the White House held an epidemic briefing in the United States. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, reminded that vaccination should be accelerated to prevent Delta from becoming a major epidemic strain in the United States. “We cannot let the epidemic increase again.”



Many countries in Southeast Asia suffer from Dleta


Due to geopolitical and border management issues, Delta has entered a number of countries around India, causing the number of infections to rise rapidly.


On May 21, the first batch of local Delta infection cases were confirmed at a construction site in Bangkok, Thailand, with a total of 36 cases. As of June 10, the Medical Department of the Ministry of Health of Thailand notified that of the 77 provinces in Thailand, 11 provinces had reported Delta infections. Supaji, director of the country’s medical department, pointed out that the department tested 4,185 confirmed cases from April to June this year and found that the number of Delta infections accounted for 8.32%. “It may become the main epidemic strain in Thailand.”


“Malaysia may be one of the countries most affected by the mutant strain.” Sin Chew Daily reported that Malaysia began to ban Indian flights from entering the country at the end of April. However, on May 1, Kuala Lumpur International Airport reported that an Indian passenger was found to be infected with Delta. According to data from the Ministry of Health of Malaysia on June 10, the basic infection rate (R0) of Labuan Island reached 1.27, the highest in the country. “The number of confirmed cases in Labuan Island remains high, mainly due to the rapid spread of the mutant strain Delta in the community and people visiting friends and gatherings during Eid al-Fitr,” said Dr. Ismuni, director of the Labuan Health Bureau.


Our World in Data data shows that in late May, Malaysia’s number of new infections per million people in a single day has surpassed India for several consecutive days, ranking first among Southeast Asian countries. “Doctors may be forced to allocate intensive care beds to patients with a higher chance of recovery due to lack of medical supplies.” Director of the Ministry of Health Nuo Xishan has repeatedly urged people to stay at home and take practical actions to support front-line medical services.


Photo caption: On June 5, hundreds of people lined up for vaccination outside a COVID-19 vaccination site in Kuala Lumpur, Malaysia. /The Star


Singapore’s “Lianhe Zaobao” stated that the current round of the epidemic in Singapore also originated from a mutant strain. On June 9, the Ministry of Health of Singapore confirmed that Delta has a stronger spread. As of May 31, a total of 550 cases of Delta infection have been confirmed in Singapore, of which 428 cases were confirmed locally.


Also since May, Vietnam has doubled the number of infections due to the spread of mutant strains. Of the country’s 63 provinces, 30 have received more than 3,000 new infections in May.


What the outside world was once worried about was that the Minister of Health of Vietnam Nguyen Thanh Long stated on May 29 that a new hybrid of the mutant strain Delta and Alpha was found in Vietnam. The characteristic of this mutant strain is that it spreads very quickly in the air. A few days later, in an interview with Nikkei Asia, WHO’s representative in Vietnam, Piao Qidong, clarified that the newly discovered mutant in Vietnam is a variant of the same lineage of Delta, not a “new hybrid strain”. He emphasized that Delta is still worrying about the epidemic in Vietnam.


Photo caption: In Shah Alam, the capital of Selangor, Malaysia, epidemic prevention personnel are collecting a swab sample from a man. Behind it is an anti-epidemic painting created by a local artist. /CNN



Against the mutant strain, vaccinating as soon as possible is the key


“The spread of Delta in the UK is out of control, but other countries seem to be at an early stage. In this case, the best response any country can do is to get vaccinated as soon as possible, while increasing daily screening and genomic testing of confirmed cases.” Bloomberg commented.


Anthony Fauci took data from the National Institutes of Health as an example. Two doses of Pfizer mRNA vaccines provide 88% protection against Delta infection; two doses of AstraZeneca adenovirus vaccines provide 60% protection. For these two vaccines, only one dose is given, and the preventive effect is 33%.


On June 8, the “Financial Times” quoted British Health Secretary Matt Hancock as saying that a retrospective study found that 126 of the country’s 12,383 Delta-infected patients required hospitalization. Among them, 83 people were not vaccinated, and only 3 people received 2 doses of the vaccine. Based on this data, it can be calculated that the protective effect of 2 doses of vaccination on Delta is about 95%. The article did not specify the type of vaccination. Since then, real-world studies by the Department of Public Health of the United Kingdom have shown that the effective rate of Pfizer/Bintech mRNA Covid-19 vaccine against Delta infection is 87.9%.


“Vaccination can effectively prevent the mutant strain from causing severe illness and reduce deaths.” On June 10, the All India Institute of Medical Sciences in New Delhi stated that 63 people infected after vaccination started a study. Among them, 10 were vaccinated with the AstraZeneca adenovirus vaccine produced in India, and 53 were vaccinated with the inactivated vaccine produced in India. Virus genetic testing was conducted on 36 of them, and 23 people were found to be infected with Delta, accounting for 63%. Of these 36 people, 19 received only one dose of the vaccine, and the rest completed both doses. The results showed that 63 people experienced 5-7 days of high fever, but no severe illness or death.


Singapore’s real-world data also proves this point. The country officially approved and widely vaccinated are two mRNA new coronavirus vaccines. Analysis shows that among the confirmed cases of infection after the completion of the two doses of vaccination, 99.2% were asymptomatic or mildly ill, 0.8% required oxygen support, and the rate of admission to intensive care was 0. Among the unvaccinated infected people, 1% were admitted to intensive care, and 0.8% died.


Photo caption: On April 9, 2021, a health worker in Bangkok, Thailand, is vaccinating Buddhists with AstraZeneca adenovirus. /AP

At present, Malaysia, Vietnam, Thailand, etc. are all stepping up vaccine procurement and vaccination speed. Malaysia has purchased 5 kinds of vaccines, saying that 80% of the population will be vaccinated by the end of October.


In order to speed up the acquisition of vaccines, Vietnamese President Nguyen Xuan Phuc sent letters to US President Biden and Russian President Putin respectively. On June 3, the country confirmed the purchase of 20 million doses of the Russian “Satellite 5” COVID-19 vaccine. Russia will transfer the technology to the Vietnamese pharmaceutical company Vabiotech, which may start producing the vaccine in July this year, with the goal of producing 5 million doses per month.


“I was one of the members of the first research group that reported the pedigree of the mutant strain B.1.617 and pointed out its risk… I have been asking myself, is there any way to predict the danger earlier, and to track and limit the mutation more quickly Strains spread?” On June 1, Anurag Agrawal published an article in Nature, reflecting on the devastating attack Delta caused to India and related enlightenment.


He said that when many countries are facing a shortage of vaccines, computer models may be used to simulate various possible variants and find the ones that are most easily transmitted in order to prepare in advance. At the same time, the screening of infection cases and the sequencing of virus genes should be strengthened and accelerated to shorten the confirmation time of new variants.




Why Delta Variant strains are so strong and can COVID-19 vaccines prevent it?


(source:internet, reference only)

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