In Social Networks
The standard mathematical definition of herd immunity applies only to "well-mixed populations," in which each infected individual is capable of transmitting the disease to any susceptible individual, regardless of social ties or location. More specifically, the relationship between the basic reproduction number R0 and the herd immunity threshold illustrated in the table above relies on a calculation that is valid only in well-mixed populations. Actual large populations, however, are better described as social networks, in which transmission can occur only between peers/neighbors. The shape of a social network can alter the level of vaccination required for herd immunity, as well as the likelihood that a population will achieve herd immunity. Compared to well-mixed populations, herd immunity in social networks is particularly fragile.
Read more about this topic: Herd Immunity
Famous quotes containing the words social and/or networks:
“Any one who knows what the worth of family affection is among the lower classes, and who has seen the array of little portraits stuck over a labourer’s fireplace ... will perhaps feel with me that in counteracting the tendencies, social and industrial, which every day are sapping the healthier family affections, the sixpenny photograph is doing more for the poor than all the philanthropists in the world.”
—Macmillan’s Magazine (London, September 1871)
“The community and family networks which helped sustain earlier generations have become scarcer for growing numbers of young parents. Those who lack links to these traditional sources of support are hard-pressed to find other resources, given the emphasis in our society on providing treatment services, rather than preventive services and support for health maintenance and well-being.”
—Bernice Weissbourd (20th century)