The outbreak of Covid in Delhi in 2021 indicates that herd immunity to delta variants is difficult: study

New Delhi: A serious outbreak of COVID-19 in Delhi this year was previously exposed to a delta variant of SARS-CoV-2 via a different variant of coronavirus, according to a study published Thursday in Science. Showing that it can infect people and highlighting the challenge, according to an international team of scientists, reaching herd immunity against mutants.Read again- Corona Third Wave: The government says it prepares for a surge in Covid cases of Rs. 450,000 to Rs. 50,000 a day. Called “important” from October to December

The study also found that the delta mutant was 30 to 70 percent more contagious than the previous SARS-CoV-2 strain in Delhi. The city has experienced multiple outbreaks in June, September and November 2020. Read again- In the horror of the third wave of Corona, Delhi Airport sees a large footprint of passengers |

The first case of coronavirus was detected in Delhi in March 2020. The situation worsened in April of this year, with daily cases increasing from about 2,000 to 20,000 between March 31st and April 16th. On admission, ICU admissions severely stressed the healthcare system, with daily deaths skyrocketing to three times the previous wave. Read again- “The third wave of corona can occur two weeks earlier in the following cases …”, ICMR warns state / UT before the festival

The authors of the study reported that Delhi’s overall seroprevalence was 56.1%, which is expected to provide some protection from future outbreaks from herd immunity.

What is herd immunity?

Herd immunity is a form of indirect protection from illness that can occur when a sufficient proportion of the population is immunized against infection. The latest study used genomic and epidemiological data with mathematical modeling to study development.

The work was led by the National Center for Disease Control in New Delhi and the Institute for Genome Integrated Biology (CSIR-IGIB) of the Institute of Science and Industry, with the participation of the University of Cambridge and the Imperial College and University Collaborators in London, UK. .. Copenhagen, Denmark.

“The concept of herd immunity is important for ending outbreaks, but the situation in Delhi is that infection with previous coronavirus variants reaches herd immunity against deltas,” said Ravi Gupta, a co-author of the study at the University of Cambridge. It shows that it is not enough to do it. “

“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. That’s it, “Gupta added.

To determine if the SARS-CoV-2 variant was responsible for the April 2021 outbreak in Delhi, the team teamed up with virus samples from Delhi from the previous outbreak in November 2020 to June 2021. Sequence and analysis of. The team found that the 2020 outbreak in Delhi was irrelevant. To a variant of concern.

Alpha mutant of coronavirus

According to researchers, the first Alpha variant identified in the United Kingdom was only occasionally identified by foreign travelers until January 2021. Alpha increased in Delhi to about 40% of cases in March 2021, but was replaced by a rapid increase in delta mutants in April, they said.

Applying mathematical modeling to epidemiological and genomic data, researchers have found that delta mutants can infect people previously infected with SARS-CoV-2.

Researchers noted that previous infections provided only 50 to 90 percent of the protection against infection by delta mutants that they provided to previous strains.

“This study helps to understand the global outbreak of Delta, including highly vaccinated populations. Delta variants are transmitted through vaccinated or previously infected individuals. It’s because we can find people who are easy to do, “says Anuraguagrawar, senior author and co-author of CSIR-IGIB. Principal researcher of research.

To find actual evidence of reinfection to support modeling work, researchers examined a group of people recruited by 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%, suggesting a very high rate of second wave outbreaks in the country. 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 breakthrough cases of vaccination at a single center during the study period, they were more vaccinated than non-delta strains of the 24 cases reported. We have found that it is seven times more likely to lead to a breakthrough infection inoculation.

(With input from PTI)