Herd Immunity And COVID-19

Updated: Feb 11

What is immunity?

Herd Immunity And COVID-19

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 towards 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.

Now, if an already immunized person contacts this disease in near future, the immunological system will be able to recognize and immediately produce antibodies that are required for combating it. Of both types of immunity, the ‘active type’ immunity is considered to have a long duration and lasts for an entire lifetime.

Passive Immunity is achieved whenever a particular individual is administered antibodies against disease in contrast to producing them through their body’s immune systems. For example, the newborn baby will acquire passive immunization from his or her mother through placental connection and one can also acquire passive immune status by getting exposed to blood products that contain antibodies like immunoglobulins that may be provided whenever immediate protectiveness from any specific disease is required.

The major advantage related to developing passive immunity is the immediate protection provided by it while on the other hand, development of active immunity requires time that can last up to numerous 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?

Develop Herd Immunity And COVID-19

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 response towards 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. On the other hand, the acquired arm of the immunological system along with the innate system synthesizes proteins called ‘antibodies’ working against any specified invading organism.

All antibodies are produced by phagocytic cells termed as ‘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 against COVID-19

Herd immunity is also known as 'population immunity'. It provides protection from any infectious disease that might occur whenever any population shows immunity either utilizing vaccination or inherent immunity that develops after getting exposed to an infection. The World Health Organization advocated the achievement of 'herd immunity' by the means of the vaccination process and thus limiting the spreading of disease in any particular segment of a population, as this results in an unnecessary increase in numbers of cases as well as deaths.

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 by the process of immunization.

SARS Covid-19 Treatment

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 against the currently available vaccines. Over 60% of the world population was infected by the year 2020. As per a few of the estimates by health care agencies, this high infection rate might have been adequate for achieving the threshold of herd immunity in a given population, however, a continued resurgence in covid-19 has shown failure in the immune response. This sudden spike in the numbers of COVID-19 cases has been seen following the emergence of newer variants such as P.1 and Omicron. This has suggested that any previous exposure to infections may not confer all-around protection against this virus.

One must also understand that there might be a greater rate of immunity in any given population that can create selective development of pressure favoring the growth of other variants that may be capable of infecting 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.

Vaccinating masses produce newer pressures on the evolution that might be able to produce newer variants, hence, it is justifiable to build the required infrastructure as well as devise newer processes for monitoring these.

Performing any calculation for analyzing ‘herd immunity’ is done after considering two major sources of immunity a) Vaccines and b) Exposure to infection naturally. People who are infected with SARS-CoV-2 develop immunity towards this virus, for how long this immunity can last is a major question. Healthcare individuals and Centric Healthcare advise people to maintain vigil and maintain protective measures against this virus since the immunity attained might reduce with time, however, one must be assured that the immunity levels do not drop to zero completely.

Does herd immunity occur in children?

Various healthcare agencies have predicted that herd immunity cannot be achieved unless children get vaccinated for this reason few vaccines have been given authorization during emergency use among children aged between 5 to 15 years with complete approval in those aged 16 years and above.

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 especially if one comes into contact with infected individuals, maintaining social distance, and washing hands frequently. If one considers the fact that immunity achieved by infection lasts for a short period such as a few months, one must follow the deadlines for vaccination at a frequent interval. 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

28 views0 comments

Recent Posts

See All