Coronavirus Outbreak Explained: What Is Herd Immunity And Can It Control The Coronavirus Pandemic?

New Delhi: The current COVID-19 pandemic is still expanding its reach even though most countries across the world have restrictions in place including strict lockdowns and social distancing norms to cut down the spread of the virus. Based on what experts know about the novel coronavirus, can a phenomenon called ‘herd immunity’ be an answer to this crisis? The United Kingdom and the Netherlands were the first countries to take herd immunity approach in dealing with COVID-19. However, the World Health Organisation (WHO) has warned that “herd immunity” strategy is experimental at best and dangerous at worst. National health organisations like National Institute of Epidemiology, Indian Council of Medical Research (ICMR) and Public Health Foundation of India (PHFI) have also highlighted that this process could harm a large number of individuals. The UK has now given up on its herd immunity building approach.

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NDTV spoke to some experts to understand what is this phenomenon and what role can it play, if at all, in overcoming the SARS-CoV-2 virus.

According to Dr. Ambarish Dutta, Associate Professor, Indian Institute of Public Health (IIPH) Bhubaneswar, herd immunity is a uniform amount of immunity that at least 60 per cent of the population in a community, in case of COVID-19, must develop to slow down the spread of infection. He said,

When enough of the population is resistant to a germ, its spread stops naturally because not enough people are able to transmit it.

How Can A Country Achieve Herd Immunity?

According to Dr. Dutta, herd immunity can be achieved in two ways. The first way is through mass vaccinations, which for COVID-19, is still under development. The second way is through the infection which means that a person gets infected and after a while, they develop antibodies to fight the infection and thus become immune to it. Since currently, the vaccine for COVID-19 is absent; countries around the globe like, the United Kingdom, the Netherlands, Sweden and Holland are experimenting with the second method.

Elaborating on the phenomenon, Dr. Rakesh Sahay, Endocrinologist and Diabetologist, and Professor at Osmania Medical College in Hyderabad, said that there are a large number of people who are asymptomatic – who show no symptoms at all or have just mild symptoms like mild fever, mild cough. Most of these people will recover from the virus without getting hospitalized, he said. This will contribute to increasing the herd immunity, Dr. Sahay added. He said,

Once a lot of people develop the infection, about 80 per cent of them have mild symptoms but they overcome the virus and develop immunity. This happens as Immunoglobulin M (IgM) levels increase in their body initially and then Immunoglobulin E (IgE) levels. IgM is mainly found in blood and is the first antibody that the body makes when it fights a new infection. IgE is normally found in small amounts in the blood but the number may be higher when the body overreacts to allergens or is fighting an infection from a parasite. This immunity helps in preventing re-infections and when a large extent of the population develops this immunity then the risk of new infection or cases decrease.

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Risks Involved in building herd immunity through infections

While it may prove to be effective in the long run, shooting for herd immunity right away would be a dangerous strategy especially because there is no vaccination, according to experts. This is because a large number of people will become severely ill causing a sudden boom in sick people needing hospital or ICU (Intensive Care Unit) care, ventilators or oxygen support which will overwhelm the healthcare system of the country.

Dr. Dutta pointed out that the effectiveness of herd immunity approach for a country will depend on the structure of the population of that country. He said,

In India, the dominating population is of youth. Young people are generally healthier with a stronger immune system than the elderlies. They can fight with the infection and build immunity against it in a much faster way. This is true with any kinds of viral infection. However, in Europe, much of the population is older because of which these countries there have experienced more severity and more fatality as far as COVID-19 is concerned. Since the immunity is low among most of the population, depending on herd-immunity through infection is not a wise step considering the gravity of the pandemic. Great Britain tried herd-immunity, it failed very badly.

Earlier in a tweet, Richard Horton, editor of the British medical journal ‘The Lancet’, also said that the British government is “playing roulette with the public”.

The UK government—Matt Hancock and Boris Johnson—claim they are following the science. But that is not true. The evidence is clear. We need urgent implementation of social distancing and closure policies. The government is playing roulette with the public. This is a major error.

— richard horton (@richardhorton1) March 10, 2020

Dr. Dutta added that countries like Sweden and Holland are also trying herd immunity. They are not discouraging the younger population from moving around. These countries, as per Dr. Dutta are taking the risk of letting the youngsters get the infection so that they can become immune to it, assuming that they have a strong immune system. However, he highlighted that there is no guarantee that they will not get severely ill or there will not be any long term effect on their body due to the infection or when they come home, they will not infect the older people in the house. Denmark is another country that is gearing up to go the ‘herd-immunity path’ and ease the lockdown currently imposed.

He said,

We don’t know enough about the novel coronavirus, SARS-CoV 2. There is a lack of evidence around the science of this virus. Thus the immunology for the virus is also not known yet.

WHO director-general Dr. Tedros Adhanom Ghebreyesus at a media briefing has also emphasized on not easing the lockdown restrictions as only a tiny proportion of the global population, maybe as few as 2 per cent or 3 per cent, appears to have antibodies against coronavirus.

The experts recommend that while the social distancing norms must remain enforced, the health authorities and policymakers should be cautious about herd immunity as there is no shortcut and the country should ideally try to achieve herd immunity through vaccination.

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