Community Immunity ("Herd Immunity")
Vaccines can prevent outbreaks of disease and save lives.
When a critical portion of a community is immunized against a contagious disease, most members of the community are protected against that disease because there is little opportunity for an outbreak. Even those who are not eligible for certain vaccines—such as infants, pregnant women, or immunocompromised individuals—get some protection because the spread of contagious disease is contained. This is known as "community immunity."
In the illustration below, the top box depicts a community in which no one is immunized and an outbreak occurs. In the middle box, some of the population is immunized but not enough to confer community immunity. In the bottom box, a critical portion of the population is immunized, protecting most community members.
The principle of community immunity applies to control of a variety of contagious diseases, including influenza, measles, mumps, rotavirus, and pneumococcal disease.
Credit: NIAID
http://www.vaccines.gov/basics/protection/
Herd immunity or herd effect, also called community immunity, describes a form of immunity[1] that occurs when the vaccination of a significant portion of a population provides a measure of protection for individuals who have not developed immunity.[2] Herd immunity theory proposes that, in contagious diseases that are transmitted from individual to individual, chains of infection are likely to be disrupted when large numbers of a population are immune or less susceptible to the disease. The greater the proportion of individuals who are resistant, the smaller the probability that a susceptible individual will come into contact with an infectious individual.[3]
http://en.wikipedia.org/wiki/Herd_immunity
When a critical portion of a community is immunized against a contagious disease, most members of the community are protected against that disease because there is little opportunity for an outbreak. Even those who are not eligible for certain vaccines—such as infants, pregnant women, or immunocompromised individuals—get some protection because the spread of contagious disease is contained. This is known as "community immunity."
In the illustration below, the top box depicts a community in which no one is immunized and an outbreak occurs. In the middle box, some of the population is immunized but not enough to confer community immunity. In the bottom box, a critical portion of the population is immunized, protecting most community members.
The principle of community immunity applies to control of a variety of contagious diseases, including influenza, measles, mumps, rotavirus, and pneumococcal disease.
Credit: NIAID
http://www.vaccines.gov/basics/protection/
Herd immunity or herd effect, also called community immunity, describes a form of immunity[1] that occurs when the vaccination of a significant portion of a population provides a measure of protection for individuals who have not developed immunity.[2] Herd immunity theory proposes that, in contagious diseases that are transmitted from individual to individual, chains of infection are likely to be disrupted when large numbers of a population are immune or less susceptible to the disease. The greater the proportion of individuals who are resistant, the smaller the probability that a susceptible individual will come into contact with an infectious individual.[3]
http://en.wikipedia.org/wiki/Herd_immunity