Herd Immunity is when the majority of a population is immune to an infectious disease, providing indirect protection to those who are not immune. This happens when a large percentage of a population has either been infected or vaccinated. Once 70%-90% of a population has such an immunity, those who can’t be immunised such as small children, and those with weakened immune systems, are at a lower risk of being infected. (https://bit.ly/2X8tK1W, https://bit.ly/2XanAhY)