Herd Immunity is a form which occurs when a large percentage of a population has become immune to an infection, whether through vaccination or previous infections so as to provide indirect protection against an infectious disease and can measure protection for individuals who are not immune to the infection .The Basic Reproduction number (R0) is an important term which helps calculation to calculate the capability of an individual to infect an individual further and enables to discover the

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... um amount of population coverage immune to develop herd immunity of that specific disease . When a critical proportion of the population becomes immune, called the herd immunity threshold (HIT), the infectious disease may no longer persist in the population, ceasing to be endemic at the end. Social networks however undergo constant growth, and it may be argued that network growth may change the level of herd immunity present in social networks. Vaccination helps prevent circulation of the infectious agents in susceptible population. High uptake and more effective the vaccine is more are the chances of success to eradicate infectious diseases like in the case of smallpox and polio. Herd immunity's inclusion in vaccination programmes makes it more favorable in cost-effectiveness or cost–benefit ratios and an increase in the number of disease cases avoided by due to vaccination. Herd or also known as Population Immunity is highly debatable subject and had different views by researchers regarding achievement of herd immunity in any disease control approach. In this article we have tried to enlighten the concepts regarding herd immunity; the diseases which can be accounted with it; its link with vaccination strategies and part of the disease eradication.