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The outbreak of Delhi highlights the challenge of reaching herd immunity in the face of delta variants.

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The serious outbreak of COVID-19 in Delhi, India in 2021 is not only that the delta variant of SARS-CoV-2 is highly contagious, but also that individuals previously infected with different variants of the coronavirus. An international scientist writing that he has shown that he may be infected with Chemistry..

SARS-CoV-2 spread throughout India in the first wave, with the first results of the Indian Medical Research Council showing 1 in 5 adults (21%) and 4 adolescents aged 10 to 17 years. 1 person (25%) was found. I was infected. This number was much higher in the big cities of India. By February 2021, more than half (56%) of individuals in Delhi were thought to have been infected.

Since the first case of COVID-19 was detected in Delhi in March 2020, the city has experienced multiple outbreaks in June, September and November 2020. After reaching a maximum of about 9,000 cases daily in November 2020, the number of new cases has steadily decreased. There are few new infections between December 2020 and March 2021.

The situation reversed dramatically in April 2021 from about 2,000 to 20,000 per day between March 31st and April 16th. This, accompanied by a rapid increase in hospitalizations and ICU admissions, put serious stress on the health care system and daily mortality surged to three times the level of the previous wave.

In a study published today, an international team of scientists used genomic and epidemiological data with mathematical modeling to Outbreak.. The work was led by the National Center for Disease Control in India and the CSIR Institute for Genome Integrated Biology, along with collaborators from the University of Cambridge, Imperial College in London, England, and the University of Copenhagen in Denmark.

The team is working on a virus from Delhi from the previous outbreak in November 2020 to June 2021 to determine if the SARS-CoV-2 variant was responsible for the April 2021 outbreak in Delhi. We sequenced and analyzed the samples. Variants of concern. The Alpha Variant (B.1.1.7) was only occasionally seen by foreign tourists until January 2021. Alpha variants increased to approximately 40% of cases in Delhi in March 2021, followed by delta variants in April (B.1.617.2).

Epidemiology and application of mathematical modeling to epidemiology Genome dataResearchers have found that the delta mutant, including the alpha mutant, is 30-70% more contagious than the previous SARS-CoV-2 strain in Delhi. Importantly, this model also suggested that the Delta variant could infect people who had previously been infected with SARS-CoV-2. Previous infections provided only 50-90% of the protection against infection of the Delta variant against previous strains.

To find actual evidence of reinfection to support modeling work, researchers examined a cohort of individuals adopted by the Indian Scientific and Industrial Research Council (CSIR). In February, 42.1% of unvaccinated subjects who participated in the study tested positive for antibodies to SARS-CoV-2. The corresponding figure for June was 88.5%, indicating a very high infection rate in the second wave. Of the 91 subjects infected prior to Delta, approximately one-quarter (27.5%) showed elevated antibody levels, providing evidence of reinfection.

When the team sequenced all samples of vaccination breakthroughs at a single center during the study period, they led to vaccination breakthroughs in 24 cases reported, with delta leading to more vaccination breakthroughs than non-delta strains. I found it 7 times more likely.

Dr. Anurag Agrawal of the National Center for Disease Control and Prevention and the CSIR Institute for Genome Integrated Biology in India said: “This study helps to understand the global outbreak of Delta, including highly vaccinated populations. Delta variants are transmitted through vaccinated and previously infected individuals. Because you can find people who are infected and susceptible. “

Professor Rabbi Gupta, co-author of the Cambridge Therapeutic Immunology and Infectious Diseases Research Institute at the University of Cambridge, UK, said: Not enough to reach herd immunity against delta. The only way to end or prevent the development of Delta is to use a vaccine booster that raises antibody levels high enough to infect this mutant or overcome Delta’s ability to avoid neutralization. .. “

Previous research Led by Professor Gupta, Delta Mutant It is most likely spread by the ability to evade neutralizing antibodies and increased infectivity.


Diffusion of the DeltaSARS-CoV-2 variant caused by a combination of immune avoidance and increased infectivity


For more information:
Mahesh S. Dhar et al, Genomic Characteristics and Epidemiology of a New SARS-CoV-2 Mutant in Delhi, India, Chemistry (2021). DOI: 10.1126 / science.abj9932

Quote: The outbreak of Delhi was obtained from https://medicalxpress.com/news/2021-10-delhi-outbreak-highlights-herd-immunity.html on October 14, 2021 (2021, October 14). Highlights the challenge of reaching herd immunity in the face of the sun)

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The outbreak of Delhi highlights the challenge of reaching herd immunity in the face of delta variants.

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