Sunday, 24 January 2010

Herd immunity

Not only is the anti-vaccination crowd, a.k.a. “infectious disease promotion movement,” endangering the lifes of children by denying them protection from all sorts of diseases they also influence the chance of children with sane parents of contracting these same conditions. Joseph Albietz on Science-Based Medicine explains:
Herd immunity is a fascinating effect, and one of the mainstays of a public vaccination effort.  The idea is that if enough people in the community are immune to a particular disease, then those who are susceptible will rarely come into contact with a person who is contagious, and the disease will be unable (or find it difficult) to spread.  This results in a greatly reduced risk of infection for the entire population regardless of their individual immunity.
The effect of the tinfoil hat brigade is evident:
Countless reports of outbreaks around the world consistently describe a disproportionate number of infections during vaccine-preventable outbreaks occurring in the unvaccinated.
What exactly is the risk of not vaccinating? According to Albietz two studies by a group from Kaiser Permanente of Colorado gave the following results:
Their first study found that the act of refusing to vaccinate against pertussis (whooping cough) placed children at a 23 times greater risk of contracting pertussis. That’s a 23 fold-increased risk of a disease that, in children under 12 months of age from 2000-2004 in the US caused 62.8% to require hospitalization, 55.8% to have apnea, pneumonia in 12.7%, and death in 0.8%.
 The second study showed
an 8.6-fold increased risk of infection with [varicella (chickenpox) ] that as recently as 1995 (when the vaccine was released), tallied 3,000,000 infections, 10,000 hospitalizations, 4,000 cases of pneumonia, 600 cases of encephalitis and 100 deaths per year.
 The article points out
The choice to refuse a vaccine, to “hide in the herd,” is an active decision to accept a markedly higher risk of infection, its complications, the associated medical costs and lost wages, the responsibility of spreading the disease to others should an infection occur, and to choose to undermine the very herd immunity on which we all depend.
Should you, or somebody you know, choose to ignore medical science so children can be exposed to an increased risk of dying, based on delusional believes, I suggest you read this article and don't forget to watch a very apt comment on this sort of sillyness: a beat poem by Tim Minchin!

Update: A study, regarding the efficacy of a flu vaccine, underscores the detrimental effect of not vaccinating to the entire community.
Bottom line: flu vaccines work to significantly reduce outbreaks when school aged children are vaccinated in isolated populations.
Also, Steven Novella has made an overview of the H1N1-debate.

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