Herd Immunity And COVID-19

Herd Immunity And COVID-19

Herd immunity of most people protecting all against virus concept visualized with different wooden cubes

What is immunity?

Immunity is the body’s ability to defend against any particular pathogen or disease using two mechanisms a) Active and b) Passive immunity.

Active immunity occurs whenever there is exposure to any particular disease pathogen that will trigger the body’s immunological system by producing antibodies toward the disease. Active immunity may be achieved by natural exposure or by vaccines.

‘Natural immunity’ develops after a person gets exposed to a particular disease-causing microorganism by contracting infection with the real disease while Vaccine-induced immunity’ is gained when a killed and//or weakened version of any pathogenic microorganisms is introduced through vaccination.

If an already immunized person near the future contracts a disease, the immune system will recognize it and produce antibodies that are required to combat it. Both types of immunity are considered to have a long duration.

Passive immunity is the ability to protect from disease by producing antibodies. When a baby is born, they’re exposed to their mother’s antibodies and immune cells. People exposed to blood can get protection right away.

Immunity is immediate protection that would work quickly. Active immunity requires time to build and can last up to weeks. When compared to active immunity, passive immunity lasts for a duration of fewer weeks or even months. Thus, immunity is the body’s inherent protective response towards any disease-causing microorganism.

How does one develop immunity?

Any individual may develop immunity either through their innate immune response or by an adaptive immune response. One can develop either of these immune responses when their body is exposed to various microbial organisms or in response to toxins that are released by these microbes. Both of these immunological systems function together. The innate immunological system is the rapidly acting responsive system. It is the primary responsibility of any microbe entering one’s body. It comprises of skin, cornea, and mucous membranes lining the respiratory, gastrointestinal, and genito-urinary tracts. All of these barriers may cause the creation of physically present barriers for protecting various harmful microbial organisms and parasites or cancerous cells.

The innate immunological system is genetically inherited and becomes active from the time of birth. Whenever the innate immune system recognizes any particular pathogen, it becomes active straight away. The cells belonging to the innate immune arm i.e., phagocytes surround as well as destroy the invading organisms.

All antibodies are produced by phagocytic cells termed ‘B lymphocytes’ following one’s exposure to an organism. These antibodies remain for a long time in one’s body. However, the time required for the formation of these antibodies could be lengthy. Although, following the first-time exposure, the body’s immune mechanism recognizes the invading pathogen and results in defensive steps. The acquired immunological system undergoes alterations during one’s lifetime pertaining to frequent immunizations that one receives. Various healthcare organizations including Centric Healthcare help in educating individuals about the importance of vaccination for developing herd immunity.

How effective is herd immunity against COVID-19?

Herd immunity is also known as ‘population immunity. The World Health Organization advocates for the achievement of herd immunity, which limits the spread of disease by making sure that those who are vaccinated are not the only ones with immunity. This results in fewer cases and deaths amongst the population.

Development of herd immunity directed against COVID-19 infection must be achieved by protecting individuals by vaccinating them and avoiding exposure to a particular pathogen that may cause the disease. All healthcare services including Centric healthcare also promote achieving herd immunity through the process of immunization.

Even though plans involving the roll-out of various anti-SARS-CoV-2 vaccines are facing hurdles in distribution as well as allocation, newer variations of SARS-CoV-2 have been continuously rising. Some of these variants carry higher transmissibility and demonstrate resistance to the currently available vaccines. Over 60% of the world population was infected by the year 2020. As per estimates by the health care agencies, this high infection rate might have been enough to achieve herd immunity in a given population. However, a failure in the immune response has been shown following the newest variants called COVID-19 and P.1 and Omicron. This has suggested that any previous exposure to infections may not confer all-around protection against this virus.

Sometimes people live in a selective environment that favors the selection of one variant over another that would be able to infect already immunized individuals. Performing fast vaccination in an effective manner might help prevent any novel variant from attaining broad infectivity in a population. Thus, there remains unevenness in the patterns of the roll-out of vaccines that might be creating challenges in managing the spread of COVID-19 infection. Vaccines and exposure to infection naturally provide immunity to SARS-CoV-2.

Does herd immunity occur in children?

Few vaccines have been given authorization during emergency use among children aged between 5 to 15 years. It’s unlikely herd immunity can be achieved with this decrease in vaccines.

Should preventive measures be undertaken even after developing immunity against Covid-19?

Centric Healthcare advises following preventive measures such as wearing masks even after getting completely vaccinated, maintaining social distance, and washing hands frequently. If one considers the fact that immunity achieved by infection lasts for a short period like a few months, one must follow the deadlines for vaccination at frequent intervals. Centric Healthcare educates all its patients regarding the importance of the booster vaccine whenever necessary with the passage of time.


  1. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/herd-immunity-and-coronavirus/art-20486808
  2. https://www.cdc.gov/vaccines/vac-gen/immunity-types.htm
  3. https://www.hopkinsmedicine.org/health/conditions-and-diseases/the-immune-system
  4. https://www.nature.com/articles/d41586-021-00728-2