Herd Immunity - an example

Measles is a bitch -- getting it hurts. There is a vaccine that was not available when I was a kid and I would have much preferred to get the jab instead of the disease (and yes, I have been vaccinated for Shingles). From the Wikipedia entry on Herd Immunity:

Herd immunity
Herd immunity (or community immunity) describes a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals who have not developed immunity. 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.

Vaccination acts as a sort of firebreak or firewall in the spread of the disease, slowing or preventing further transmission of the disease to others. Unvaccinated individuals are indirectly protected by vaccinated individuals, as the latter will not contract and transmit the disease between infected and susceptible individuals. Hence, a public health policy of herd immunity may be used to reduce spread of an illness and provide a level of protection to a vulnerable, unvaccinated subgroup. Since only a small fraction of the population (or herd) can be left unvaccinated for this method to be effective, it is considered best left for those who cannot safely receive vaccines because of a medical condition such as an immune disorder, organ transplant recipients, or people with Egg Allergies.

Unfortunately, this is playing out in Texas. From USA Today:

Texas measles outbreak linked to church
Measles is making a worrisome resurgence across the USA, with at least 135 documented cases this year.

Measles, once a common childhood infection that killed up to 500 Americans a year, has been officially eradicated in the Western Hemisphere. For many years, the USA's few dozen measles diagnoses were "imported" cases in individuals who traveled from countries where the virus remains common. High vaccination rates largely halted the virus at the North American border.

The country's safety net has become more porous in recent years. Although overall vaccination rates remain high, communities of like-minded parents who refuse immunizations for their children have been vulnerable to outbreaks.

The latest measles outbreak is in Texas, where the virus has sickened 25 people, most of whom are members or visitors of a church led by the daughter of televangelist Kenneth Copeland.

Fifteen of the measles cases are centered around Eagle Mountain International Church in Newark, Texas, whose senior pastor, Terri Pearsons, has previously been critical of measles vaccinations.

Asshat - endangering your congregation over bad science...