Is Herd Immunity Really Capable of Eliminating a Pandemic like COVID-19?

Saturday, July 25, 2020

In present COVID-19 situation, in which lakhs of people are being infected while thousands are losing life daily, many questions have arrived in the minds of the people about immunity and its effectiveness in curing diseases. This also intensified because data of different countries on death due to SARS-CoV-2 or COVID-19  varied at a larger extent, some countries having death rate ranging between 9%-10% while some countries having below 2%-3% almost a difference of more than 3 times. The question of immunity is also came up in minds of people due to decreasing death rate of COVID-19 disease. Some countries like Sweden has relied on immunity and didn't lockdown the country or done it partially unlike China, Italy etc.

What is Immunity?

Immunity is the ability/response of our body's immune system which produces 'Antibodies' (made up of protein) to fight against external agents like viruses, bacteria and other microbes, causing health problems. 
Immunity varies from person to person as well as on the basis of age, diet, daily routine and even the place where one lives. 
Persons of older age group generally have weak immunity. Similarly new born babies, person with comorbidity (having serious health problems already) are also on the weaker side of immunity. 

What is Herd Immunity?

Herd immunity is a stage of a pandemic in which a large group (or a majority of people) got infected from a disease causing external microorganisms such as viruses, bacteria etc. which results into the reduction of the hazards of the pandemic/disease and eventually stops. Similar thing is done by vaccination programs in which a dead or deactivated part of  disease causing virus or bacterium(which is harmless) is used to infect people so that they become immune from the disease. 
Many countries, currently in this COVID-19 pandemic are relying on this herd immunity and didn't do lockdown or done it partially or revoked it prevent their economy from going into recession.
However achieving herd immunity is an upheaval task and requires much time depending on the rate of infection. It can cause serious problem especially  when death rate of the disease and rate of infection is higher (Because of air transmission or  human to human transmission) Hence before relying on herd immunity, we should think wisely and must review health facilities in the country/region as well as the intensity of disease. 

How Antibodies are Detected?

Antibodies can be easily detected by serological tests, which identifies the antibodies present in the body against the particular diseases. Antibodies are specific for every disease.
Recently in India Serological surveys are being conducted in various parts of the country to identify the level of spread of the disease in the country. 
In one of the random serological surveys conducted by the ICMR in Delhi found that out of 21000 random samples about 23% of had antibodies against COVID-19 virus. If we apply this data on the whole Delhi about 46 lakh people out of roughly 2 crore population of Delhi is infected from the disease already.

Is it safe to Predict Effectiveness of Antibodies Detected through Serological Survey?

The simple answer would be 'NO' because the serological tests are meant only to find out whether the antibodies are present or not. The effectiveness of antibodies to fight against the disease, according to scientists depend on the the 
  1. Amount of antibodies present in a person's body, and
  2. Whether the antibodies detected are "Neutralising Antibodies" or not because only these antibodies can fight against the disease causing microorganisms.
The detection of both of these parameters are not possible through serological surveys being conducted in India or any part of the world.

What Proportion of the People is Required to be Infected to gain Herd Immunity?

According to various studies, to gain, herd immunity against a pandemic/disease require a majority of the people/generally more than 50% of the people to be infected with the Disease. But in some case like in the case of Measles about 85%- 90% people is required to be infected to attain herd immunity against the disease.
Various studies have found out that about 55%-75% of the people of the world must be infected/immunized from the COVID-19 to attain herd immunity against the disease.
There is no case of reinfection is reported till date, but some studies reported that antibodies of COVID-19 loses their effectiveness after 4 months, hence even if one achieved immunity it will not be permanent and required to be vaccinated periodically.


According to our analysis we can say that the herd immunity is not reliable at all for handling the pandemic like COVID-19. So, we should focus more on preventive measures such as social/physical distancing, use of masks, avoid visiting public places as much as possible and boosting the medical facilities by equipping hospitals with critical equipments like Nebulizer, Oxygen pulsator, Ventilators and modern Life Support Systems  which is essential for treating critical patients, as seen in the case of immune response lead  Cytokine storm, which is causing the large number of deaths.