It is believed by the experts, scientists and researchers in the field of infectious diseases that if herd immunity gets established and retained in a population for enough duration of time, the disease is predictably reduced if not completely eradicated. In other words, herd immunity puts brakes on community transmissions. Today, I Hemant Batra, the public policy speaker shall be talking about herd immunity so keep watching this video.
We have been hearing a lot about Herd immunity as the lockdown is loosening up in India and literally coming to an end. What is Herd Immunity, you must be pondering? Let me take you through this concept, which is also known as community immunity, population immunity, or social immunity. It is a kind of incidental shield or protection from infectious diseases including epidemics or pandemics which happens when a huge proportion of a population becomes immune to an infection that is resistant and protected to an infection. This immunity happens not by some miracle or random intervention of some supernatural force. It happens naturally either through immunization that is vaccination or earlier infections which build a kind of shield around those people who are not immune.
In a population in which a sizeable percentage of people acquire immunity, those people obviously are no more the cause of disease transmission. This leads to the breaking of the chains of infection leading to the slowing down of the spread of disease. The greater the number of immune persons in a population, the lesser the likelihood that non-immune or vulnerable individuals will come into contact with an infectious individual. This helps in protecting non-immune individuals from disease and infections. Herd immunity was documented as a biologically happening phenomenon in the 1930s when it was noticed that after a substantial number of children had become immune to measles, the number of new infections provisionally declined, including among susceptible children.
As I mentioned earlier that People can become immune by recuperating and recovering from a previous infection or through vaccination. However there are certain exceptions to herd immunity, some people have serious medical conditions and their immunity is low so they may become sacrificial victims in this process. Well, As Soon As a particular level or threshold gets achieved, herd immunity steadily reduces and even eradicates disease from a population. As stated in the Oxford Textbook of Infectious Disease Control, This elimination, if achieved worldwide, may result in the permanent reduction in the number of infections to zero, called eradication. For instance, Herd immunity created via vaccination contributed to the eventual eradication of smallpox in 1977 and has contributed to the reduction of the frequencies of other diseases.
This illustration shows an eruption of infection in a community in which a few people are infected (shown in red) and the rest are healthy but unimmunized (shown in blue); the illness spreads freely through the population. This image illustrates a population where a small number have been immunized (shown in yellow); those not immunized become infected while those immunized do not. In the third image, a large proportion of the population has been immunized; this prevents the illness from spreading significantly, including to unimmunized people. In the first two examples, most healthy unimmunized people become infected, whereas in the bottom example only one-fourth of the healthy unimmunized people become infected.
The model or science of Herd immunity does not apply to all viruses and infections. Basically it applies to only those that are communicable and contagious, meaning that they can be transmitted from one individual to another. Tetanus, for instance, is infectious but not contagious, so herd immunity does not apply.
The herd immunity threshold for this Covid 19 is still unclear, but many epidemiologists consider it will be achieved when between 60% and 80% of the population has been infected and develops resistance. A lower level of immunity in the population can slow down the spread of a disease slightly, but the herd immunity number represents the point where infections are significantly less likely to turn into large occurrences of infection.
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