Archive for January 22nd, 2010

You can’t hide in the herd

Can you hide in the herd?  Well, I suppose the title has given away the punch line.

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.

This has lead to the belief that because of the protection of the herd’s immunity, individuals now have the option to avoid even the minimal cost and risk of vaccination while having the same reduced risk of infection as if they had vaccinated.

Let’s set aside the fact that that there are people who have no choice but to rely upon herd immunity as their sole line of protection against these infections.  Forget that there is a threshold below which herd immunity collapses, and that our current vaccination rates tend to be right on the cusp of that threshold.  Pay no attention to the fact that the personal decision to not vaccinate deprives others of their sole protection from these infections.  Finally, ignore the ethics and self-defeating nature of benefiting from the sacrifice of others while simultaneously eroding the efficacy of the herd immunity being exploited.  On a small enough scale, doesn’t the tactic of hiding in the herd provide the same protection as getting vaccinated without incurring the minimal risk of vaccination?

Not so much. (more…)

Posted in: Science and Medicine, Vaccines

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