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What is Herd Immunity? Is it Possible to Achieve Herd Immunity in India?

With rising numbers of Covid-19 cases around the world and the possibility of a vaccine still far away, ‘herd immunity’ is a common term thrown around by health officials. While there is some compelling evidence and hope that a vaccine could be available as early as 2021, we must rely on social distancing measures and a certain amount of herd immunity for the time being.

But what exactly does it mean?

Herd Immunity 

Herd immunity, also known as community immunity, refers to immunity present in the community when a large section of the population is immune to a specific disease. If a high percentage of the population is resistant, then the bacteria or virus has nowhere to go and is thus eradicated. 

Herd immunity is of extreme importance for people who are at high risk of contracting diseases such as the elderly, small children, and immunocompromised people who cannot get vaccinated. As these high-risk people consist of a small percentage of the population, the bacteria or virus tends to peters off before it can reach them, thus protecting the population as a whole. 

Herd immunity explained

A good example of the efficacy of vaccination and herd immunity comes from the eradication of smallpox, a highly infectious and deadly disease that was completely removed from society. 

The percentage of the general population that needs to be immune to any given disease differs widely. For instance, measles is a highly infectious disease, especially among children, and it is estimated that about 95% of the population needs to be immune to interrupt or break the chain of transmission. 

How Can We Achieve Herd Immunity? 

There are two ways to achieve herd immunity: vaccination and natural infection. 


Vaccines are biological preparations that provide immunity to the recipient from infectious diseases. A vaccine for Covid-19 would be the ideal solution as vaccines do not lead to any complications, side effects, or lasting damage. However, due to the rigorous nature of vaccine testing, one for Covid-19 may not be instantly accessible.

Vaccines allow your body to recognize the virus or bacteria and develop antibodies. If you are then naturally exposed to the virus or bacteria, your body will already be prepared to fight off the disease. Compulsory vaccination can lead to herd immunity and protect high-risk people. 

However, due to misinformation, religious objections, or skepticism, many people choose not to vaccinate themselves or their families. In this case, the cumulative herd immunity levels required may not reach the threshold, and thus the virus or bacteria may continue to survive. 

An example of this is the sudden rise in measles cases in the US after the anti-vaccination movement. Prior to this, measles was on track for eradication, but a since-disproved and retracted study by a discredited physician, led to fear that the MMR (measles-mumps-rubella) vaccine leads to autism. Since then, the US has reported a dramatic rise in anti-vaxxers numbers and the reemergence of these diseases.

Natural Infection 

Another common method to achieve herd immunity is through natural infection. An example of this would be the 1918 Spanish influenza pandemic. The people who had been infected with that strain were later discovered to be immune to the H1N1 virus – an influenza subtype. 

However, there is no scientific data supporting that infection of the Covid-19 virus leads to immunization from future infections. Additionally, as the virus moves along the population, it adapts and mutates, which may lead to further infections. Conservative estimates state that about 70% of the population would need to be infected with Covid-19 for herd immunity through natural infection to kick in, which would simply overwhelm health care systems around the world. 

Although, it has been suggested that in some pockets of India, herd immunity may already be taking place. For instance, a study found that 57% of the population living in Mumbai slums have already been infected, and thus, are close to achieving natural immunization through herd immunity.

What Does This Mean for the Future? 

Herd immunity is a tantalizing subject as it involves no action. It is easy for people to sit back and rely on herd immunity as an alternative to vaccination, but it masks the millions of lives lost and permanently affected due to infections. 

Even after months of research, we do not know the lasting effects of a Covid-19 infection. Millions of lives have already been lost all over the world due to the reliance on herd immunity, inaction, and misinformation. 

Now, it is on us to ensure that we stop these numbers from rising. To do this, we have to start being considerate to ourselves, our loved ones, and society as a whole. We must follow social distancing measures, always have a mask on when leaving the house, wash our hands multiple times a day for at least 20 seconds, and keep ourselves up-to-date on Covid-19.

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