Vaccination and herd immunity
Summary of Vaccination and herd immunity
When the majority of a population is vaccinated against a certain disease, the entire community is resistant to attack by the disease, including those unvaccinated, due to herd immunity. Herd immunity only works when the disease is contained to a single host species, and transmission occurs directly from one member of the host species to the other.
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![VACCINATION & HERD IMMUNITY osms.it/vaccination-herd-immunity HERD IMMUNITY BASICS ▪ Herd immunity: phenomenon in which entire population is indirectly protected against disease when critical percentage of members are immune ▫ Immunity can be innate/acquired through vaccination/by naturally recovering from infection ▫ The higher the proportion of immune people in a population, the less likely the encounter between a susceptible person and an infected one → chain of infection is disrupted Conditions ▪ Host is a single species ▪ Transmission of the organism must be spread by direct contact ▪ No reservoir outside the human host ▪ Infections must induce solid immunity 54 OSMOSIS.ORG HERD IMMUNITY & COMMUNITY HEALTH ▪ The critical percentage of immune individuals needed to achieve herd immunity varies according to disease contagiousness (e.g. 94% in measles [highly communicable] → increased number of individuals need to be immune) ▪ Because of herd immunity, vaccination programs do not necessitate yield 100% immunization rates, yet can achieve highly effective protection by immunizing critical percentage of a population ▪ Herd immunity is important for public health because individuals who cannot develop immunity or cannot be vaccinated depend on herd immunity (e.g. newborn infants, individuals with immunodeficiency due to HIV/AIDS, cancer, cancer treatments)](https://d16qt3wv6xm098.cloudfront.net/nrtkgGsRTX_g8U283Mzg2QjtT926TQIE/thumb-3.jpg)
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