Science

Asymptomatic Covid-19 cases could hold the key to ending pandemic: Report

Hemani Sheth Mumbai | Updated on August 09, 2020 Published on August 09, 2020

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Asymptomatic Covid-19 cases could be the key to understanding how a larger population can develop immunity against the virus, according to a report by the Washington Post.

The report cites the research of Monica Gandhi, Professor of Medicine and Associate Division Chief (Clinical Operations/ Education) of the Division of HIV, Infectious Diseases, and Global Medicine at UCSF/ San Francisco General Hospital.

Globally, over 19 million people have been infected by Covid-19. Of these, more than 7 lakh people have succumbed to the infection. Gandhi’s research focuses on asymptomatic cases, which form a larger part of the infected cases.

“It is an intriguing hypothesis that asymptomatic infection triggering immunity may lead us to get more population-level immunity,” Gandhi said as quoted by the report. “That itself will limit spread.”

According to the United States Centres for Disease Control and Prevention’s latest estimates, 40 per cent of people infected with Covid-19 are asymptomatic.

Further research into why a large number of people infected with the virus show no symptoms and the overall diversity of the illness, can help researchers better understand pandemic control measures, the report said. It can help in developing therapeutics and vaccines as well as get a better insight into how it may possibly create a pathway to herd immunity, said the report.

Existing immunity

Studies into a larger population having existing immunity may also help better understand why a larger part of the population develops almost no symptoms.

Some studies focused on “T-Cells” memory states that people already have some sort of pre-existing immunity against the virus. These studies state that people may have some degree of existing immunity against SARS-CoV-2 by having been exposed to other coronaviruses such as a common cold.

Alessandro Sette, Shane Crotty and others at the La Jolla Institute for Immunology near San Diego have conducted a significant study that has been published in Nature Reviews Immunology.

“T cell reactivity against SARS-CoV-2 was observed in unexposed people; however, the source and clinical relevance of the reactivity remains unknown. It is speculated that this reflects T cell memory to circulating ‘common cold’ coronaviruses. It will be important to define the specificities of these T cells and assess their association with COVID-19 disease severity and vaccine responses,” the study said.

By analysing blood samples of people recovering from Covid-19 and comparing it with samples from uninfected individuals collected between 2015 to 2018, the researchers found that in 40 to 60 per cent of the old samples, the T cells seemed to recognise the novel coronavirus and respond accordingly.

Other researchers claim that pre-existing vaccines such as the BCG (Bacille Calmette-Guerin), a vaccine for tuberculosis (TB) disease, is also effective in containing the infection by evoking immune responses.

Research published in one of the journals of the non-profit American Association for the Advancement of Science stated that the BCG vaccine slows down the rate of infection and death rate in Covid-19 patients.

Premature theories

The opinion that asymptomatic cases may hold the key to developing immunity contradicts experts, who suggest that people must be wary of asymptomatic cases.

According to the US CSC, the transmission rate from asymptomatic cases is 75 per cent.

According to US virologist and expert Dr Anthony Fauci, these “theories” regarding why a majority of people develop almost no symptoms or mild symptoms are relatively premature.

“There are so many other unknown factors that may determine why someone gets an asymptomatic infection,” Fauci said as quoted by the Washington Post. “It’s a very difficult problem to pinpoint one thing.”

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Published on August 09, 2020
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