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Wednesday, October 28, 2020

Covid-19 vaccine tracker, October 13: Herd immunity ‘scientifically and ethically problematic’ concept, says WHO

Coronavirus (COVID-19) vaccine update, October 13: Recently, three well-known scientists released a declaration, recommending an approach called "Focussed Protection" based on the concept of herd immunity.

By: Explained Desk | Pune | Updated: October 21, 2020 11:11:45 am
herd immunity, WHO on herd immunity, scientists declaration on herd immunity, what is herd immunity, coronavirus vaccine, india covid 19 vaccine, indian expressStudents arrive at S P College in Pune to write their final year examinations. (Express Photo: Ashish Kale)

How is this pandemic likely to end? Through universal vaccination, or through herd immunity, when sufficiently large proportion of population get infected with the virus and generate natural immunity against the disease?

Several scientists believe that the pandemic might come to an end sooner, and with lesser painful economic consequences, if it was allowed to spread rapidly in the population, while shielding the elderly and the vulnerable. These are the advocates of herd-immunity approach, and have been arguing that interventions like movement restrictions and lockdowns only manage to slow down the pandemic, not bring an end to it, while prolonging the hardships and economic misery of the people. The unintended consequences of such interventions, they argue, might be having the effect of medicines being more harmful than the disease they are trying to cure.

Recently, three well-known scientists — Sunetra Gupta, an epidemiologist at Oxford University, Jay Bhattacharya, a professor at Stanford University Medical School, and Martin Kulldorff, professor of medicine at Harvard University — released a declaration, expressing “grave concerns about the damaging physical and mental health impacts of the prevailing Covid19 policies” of governments across the world, and recommended an approach called “Focussed Protection” based on the concept of herd immunity.

The declaration, which has so far garnered signatures of nearly 9,000 medical and public health scientists, and over 22,000 medical practitioners apart from close to four lakh other people, says current policies, based on restrictions on human interactions and activities, if persisted with till a vaccine becomes widely available, would “cause irreparable damage, with the underprivileged disproportionately harmed”.

Instead, the declaration recommends, those who are not vulnerable should immediately be allowed to resume their normal life, though with adoption of physical distancing norms, schools and colleges should reopen, young and low-risk adults should be allowed to work from office, restaurants and other businesses should open, arts, music, sports and cultural activities should resume. Only the elderly and vulnerable sections of the population need to be shielded, and isolated. The declaration points out that the vulnerability to death due to Covid19 was “more than a thousand-fold higher” in the old and infirm than the young.

“The most compassionate approach that balances the risks and benefits of reaching herd immunity, is to allow those who are at minimal risk of death to live their lives normally to build up immunity to the virus through natural infection, while better protecting those who are at highest risk. We call this Focused Protection,” the scientists say in the declaration.

“We know that all populations will eventually reach herd immunity — i.e. the point at which the rate of new infections is stable — and that this can be assisted by (but is not dependent upon) a vaccine. Our goal should therefore be to minimize mortality and social harm until we reach herd immunity,” they say.

Also read | J&J pauses Covid-19 vaccine trials due to unexplained illness in participant

The scientists also released a video, in which they answered some of the questions about the declaration. Bhattacharya said it would be wrong to say they were recommending the “herd immunity strategy” to the pandemic.

“Herd immunity is not a strategy. Herd immunity is a fact about most of the infectious diseases. Even if we were to have an effective vaccine, we would be relying on herd immunity as the end point. It is less of a strategy, than a recognition of a biological fact.” Bhattacharya said.

“Our aim is not to say lets do nothing. I think that is the misconception people have when they hear the phrase herd immunity strategy. In fact, it is quite the opposite. Our strategy involves protecting the vulnerable. We have learnt a lot about this disease in last six to eight months. In particular, we have learnt what groups are more vulnerable to this virus… Our strategy takes advantage of the knowledge we have gained about this virus, and proposes concrete ways to protect the vulnerable, while minimising the collateral damage,” he said.

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But, in the clearest stand it has taken so far against this approach, the World Health Organisation, on Monday, said herd immunity was “scientifically and ethically problematic”. It said countries must continue to do what they have been doing to deal with the pandemic, only more effectively. It wasn’t clear whether WHO was specifically responding to the declaration released by the three scientists.

“Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic. It is scientifically and ethically problematic,” WHO director general Tedros Adhanom Ghebreyesus said at a press conference.

He went on to elaborate on his argument. “First, we don’t know enough about immunity to Covid19. Most people who are infected with the virus that causes Covid19 develop an immune response within the first few weeks, but we don’t know how strong or lasting that immune response is, or how it differs for different people. We have some clues, but we don’t have the complete picture. There have also been some examples of people infected with Covid19 being infected for a second time,” Ghebreyesus said.

“Second, the vast majority of people in most countries remain susceptible to this virus. Sero-prevalence surveys suggest that in most countries, less than 10 per cent of the population have been infected with the Covid19 virus. Letting the virus circulate unchecked, therefore, means allowing unnecessary infections, suffering and death,” he said.

“And although older people and those with underlying conditions are most at risk of severe disease and death, they are not the only ones at risk. People of all ages have died,” he said.

Ghebreyesus said the right way to reach herd immunity was by vaccinating more and more people.

“Herd immunity is a concept used for vaccination, in which a population can be protected from a certain virus, if a threshold of vaccination is reached. For example, herd immunity against measles requires about 95 per cent of a population to be vaccinated. The remaining 5 per cent will be protected by the fact that measles will not spread among those who are vaccinated. For polio, the threshold is about 80 per cent. In other words, herd immunity is achieved by protecting people from a virus, not by exposing them to it,” he said.

WHO has been backing the development of vaccines, and has launched an initiative to expedite the development, production, and equitable distribution of these vaccines.

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