With migrants heading home, some experts call for herd immunity to combat coronavirus crisis but others warn it is no panacea

Where some see crisis, others see opportunity. Some experts have been advocating another method of fighting the coronavirus: Herd immunity. But what is it? And why is it so controversial?

Manasi Chandu May 18, 2020 09:58:17 IST
With migrants heading home, some experts call for herd immunity to combat coronavirus crisis but others warn it is no panacea

On 29 April, the Centre allowed migrant labourers to return to their home states and issued strict guidelines in terms of social distancing and quarantine rules. The Indian Railways operated the first train ferrying migrants back to their native states on 1 May and Shramik Special trains have since transported 17 lakh labourers home.

Earlier, host states faced the challenges of providing food and shelter for migrant labourers, and of convincing them of the necessity of staying where they were. Now, there is a new fear: of the coronavirus spreading in rural areas that have remained relatively untouched.

Experts have expressed concern about community transmission and a lack of healthcare infrastructure in rural areas even as Odisha, Bihar, Rajasthan and Jharkhand have seen a spurt in cases with the influx of migrant workers.

Dr Kumudini Panigrahi, an associate professor in the Department of Microbiology at KIMS, Bhubaneswar, told Firstpost returning migrants would invariably lead to the infection spreading. "Even after quarantining them for 14 days upon arrival, the incubation period of the virus might increase and they might be infected post quarantine. Since it is such a new virus, it's hard to say how it will  act at any given point of time," Dr Panigrahi said.

Dr Kiran Dave agreed. The vascular surgeon from Ahmedabad said it was difficult to determine who was infected due to the large number of asymptomatic cases. "Migrants may end up infecting people in their villages, leading to community transmission, which is a big issue due to the lack of any medical facilities and an already burdened healthcare system," Dr Dave said.

Herd immunity 

However, where some see crisis, others see opportunity. Some experts have been advocating another method of fighting the coronavirus : Herd immunity. But what is it? And why is it so controversial?

Herd immunity is a scientific concept that states that if a majority of people in a population are exposed to a microbe, the whole group would become develop immunity on their own and hence be immune to the virus, regardless of the presence of some susceptible people. This is because the microbe does not have an easy way to transmit anymore. So, the majority of immune people will, in a way, save the susceptible ones.

The traditional way of establishing herd immunity to a virus is simple: Vaccinating an overwhelming majority of the population. Take measles and polio, where 90 to 95 percent and 80 to 85 percent of the populace respectively had to be vaccinated to establish herd immunity. Polio has been eradicated in India.

And in the absence of a vaccine? Letting 60 to 70 percent of the population contract the infection and let the virus run its course.

'Only way forward'

Some high-profile experts have argued that India has no choice but to establish herd immunity. Jayaprakash Muliyil, chairman of the Scientific Advisory Committee of the National Institute of Epidemiology has called it the "only way forward."

In an interview with The Wire, Dr Muliyil said the lockdown meant India was not trying to confront the virus, but to "hide from it". Once the lockdown is lifted, the virus, which has not disappeared, will hit us again, Dr Muliyil argued.

Dr Muliyil proposed that India's young population expose themselves to the virus and build up immunity, saying the country's young demographic profile gives it an advantage over the United States, Italy, Spain, France and the UK.

He added that a good guesstimate is that approximately 60 percent of India's youths would have to acquire immunity for herd immunity to be established.

Immunologist and cell biologist Dipyaman Ganguly told News18  with no hopes of vaccine in the near future, herd immunity is one of the only hopes of defeating the coronavirus .

Ganguly, principal scientist and Swarnajayanthi Fellow at the CSIR-Indian Institute of Chemical Biology (IICB) is currently working on Randomised Control Trial (RCT) using convalescent plasma collected from patients who have recovered from COVID-19 , said,"Since developing a vaccine for COVID-19 is not an easy task and it is unlikely that we will get one soon, the only hope that remains is that of herd immunity and it is bound to happen.”

“The virus is going infect a large number of populations in India. When a large number of people get infected, their bodies will develop natural immunity. They will stop the virus from spreading further by breaking the chain of infections transmitted from one person to another," he told the channel.

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Representational image. AP

No magic bullet

Of course, such a strategy is rife with risk. The first problem is that, in the absence of a vaccine, herd immunity is by no means a magic bullet. Dr Gyaneshwar Rao, a senior practising surgeon explained, "Herd immunity is a scientific concept, not a goal or a strategy. It is a part of any infective epidemic or pandemic."

He explained that herd immunity is measured with the ease with which a disease spreads (infectious virus or microbes) and is measured using the ‘reproduction number’ (R0), which is the average number of people who are expected to catch the disease from a single infected person. For COVID-19 , R0 is estimated to be around 2 to 3. While the common flu, in comparison, has an R0 of 1.3, while measles has an R0 as high as 18.

Dr Michael Ryan, executive director of the WHO’s health emergencies programme, has warned against thinking that countries could "magically" make their populations immune to the coronavirus and to consider the human cost it could entail. “We need to be careful while using terms in this way around natural infections in humans because it can lead to a very brutal arithmetic which does not put people, life and suffering at the centre of that equation,” Ryan added.

Which brings us to the second problem of putting your chips down on such a strategy. India's fatality rate is currently 3.23 percent compared to the global average of 6.28 percent. Let's be generous and stipulate that the mortality rate falls to 1 percent.

Letting the virus spread far and wide in a country as populous as India, even in a controlled manner (were such a thing possible) before herd immunity could conceivably be established could result in lakhs of deaths.  Dr Muliyil, in the interview with The Wire, agreed. Even as he proposed isolating the elderly from the infected,  he said such deaths would be "the cost to be paid to keep the rest of India safe" and "the sacrifice" India is asking of its youths so the country could survive.

Speaking to Firstpost, Dr Harsh Toshniwal, an infectious diseases specialist in Ahmedabad, broke down the numbers entailed in employing such a strategy, "Herd immunity isn't just people getting infected and recovering. If 60 to 70 percent of the population get infected, recover, become immune, and then transmit that immunity to the rest 40 to 30 percent indirectly, that is when we can say herd immunity by infection has been achieved. In a country of 130 crore, that would mean around 90 crore people being infected. That is a huge number which our healthcare system is not ready to take on, even if most of these cases are not serious."

He noted that if even 90 crores Indian were infected, about half (45 crores) would be asymptomatic and the rest symptomatic. "Where will we get the beds, the doctors, the nurses, ventilators to treat these sympathetic patients? It would be absolutely devastating to our country. Herd immunity through vaccination is the only method that can work. We cannot afford to infect people. "

Dr Toshniwal also gave an example: "Polio was eradicated by giving vaccines to 80 percent of the children in India, which indirectly provided immune protection to the remaining 20 percent. But herd immunity by infection in India would devastate our healthcare infrastructure."

Sweden all-in, UK backtracks

In Sweden, which is all-in on herd immunity through spreading the virus, colleges and high schools were kept closed, but kindergarten through grade nine open. This strategy has been controversial, with the country's coronavirus death rate per million citizens higher than that of the United States (which is leading the world's coronavirus toll), and its coronavirus toll is considerably higher than its Nordic neighbours, which all enforced stricter lockdown measures, as reported by The Guardian.

Meanwhile, the UK, which initially seemed to be heading in that direction, quickly backtracked and introduced stringent social-distancing measures after new simulations of the outbreak from Imperial College London highlighted how badly hospitals would be overwhelmed by such a strategy and the government realised the number of deaths it would entail.

Comparing India with Sweden and the United States is like comparing apples to oranges, others said.

Dr Om Shrivastava, a consultant with the National Centre for Disease and Control told Firstpost, "The vast majority of people in India do not have the same access to clean water, sanitisation, healthcare facilities. One needs to evaluate these things and account for the amount of exposure an individual has to viruses on a daily basis. Unlike Sweden, where most people have equal access to healthcare, food and water, all Indians do not have the same access and that is a major issue".

Dr Vinit Lal, an interventional cardiologist based in the US, told Firstpost, " Although the US is currently not looking into this strategy but it is waiting for developing nations like India, which has a younger population to see how this works with such a new virus like COVID-19 . It's an attractive option, but a rather risky gamble. But that being said, no country in the world is an expert on this virus to tell us if this concept can work."

With a COVID-19 vaccine — the only fool-proof method of keeping everyone safe — being at least 18 months away, and with governments weighing the best way to protect both lives and livelihoods, the debate over herd immunity is only set to grow louder and fiercer.

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