
California schools' risks rise as vaccinations drop - kqr2
http://www.latimes.com/news/local/la-me-immunization29-2009mar29,0,3148179.story
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tom
The fact that so many parents are basing the medical decisions they make for
their children on results that have been proven over and over to be wrong,
false or misinterpreted and the well meaning, but scientifically unfounded
spouting of Jenny MacCarthy amazes me. Unfortunately the main stream media
(wow, I can't believe I just typed that) has a tendency to latch on to
correlation studies because they are easy to understand and spin, not because
they are right.

I've spent much of the last 4 years of my life studying the state of the
research of Autism and neurological diseases and disorders. Does Autism scare
the crap out of me? Heck yeah! Did I immunize my 10 month old boy - yes. Did
every member of my lab immunize their sons and daughters - yes. There's a
correlation study for you - 100% of our group of researchers who are better
read than 99.99% of the world on Autism and the state of Autism research
immunized ALL of their children. I can't wait to be on the cover of TIME!

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cryptoglyph
Regardless of reason, the parent has the ultimate right to decide for his and
her children. The government takes a back seat. True liberty lies in the
capability to make decisions that the majority disagrees with.

Besides -- if these children do catch communicable diseases, and your children
are vaccinated, what are you worried about?

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endtime
Something I've never understood: If immunization prevents you getting a
disease, and you are immunized, why are you worried about catching the disease
from people who aren't immunized?

I'm aware the the above may be an oversimplification and someone might have a
good explanation - that would be most welcome.

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timr
Two reasons:

First, no vaccine is 100% effective. You can be vaccinated for something, yet
still get the disease if you're exposed consistently, or with a great
intensity. Thus, the goal of most vaccinations is to achieve "herd immunity",
wherein enough people within a population are vaccinated that the chance of
any person being exposed to a case of the disease is low enough that even an
imperfect vaccine can be considered 100% effective.

If herd immunity is not achieved, then even the best vaccines will fail to
protect some percentage of the population. Outbreaks will occur, and
vaccinated people will succumb; in particular, people with weakened immune
systems, the elderly, and pregnant women are susceptible to diseases, even
when vaccinated.

Second, for some diseases -- such as chickenpox and rubella -- incomplete
immunization of a population actually results in _worse_ epidemics, because
the incomplete immunization of a population tends to shift the cases of the
disease to older people. And for diseases like chickenpox and rubella,
childhood infection is relatively innocuous, whereas infection as an adult can
_kill_ you.

This latter concern isn't merely hypothetical -- there was a recent example of
the consequences of incomplete vaccination in Greece, in the early 1990s.
Because the Greeks had only inconsistently vaccinated for rubella starting in
the 60s, there was a huge outbreak of adult rubella infections in 1993, and as
a result of that, there was an epidemic of rubella-related spontaneous
abortions and birth defects (a condition known as congential rubella syndrome,
which is a hideous disease that the rubella vaccine was arguably intended to
prevent). Had the immunization rate for rubella been high enough to achieve
herd immunity, this never would have happened.

~~~
endtime
Thanks for explaining. The first reason makes sense. The second doesn't,
though. I understand that if an entire generation wasn't immunized, then that
generation is susceptible when they are old (as at any age), but I don't see
why, in the general case, older people would be more vulnerable.

~~~
timr
If you only immunize 50% of each generation against a virus, then you slow the
transmission rate of the virus, but you also allow the number of susceptible
individuals to grow over time. Eventually, the number of susceptible
individuals reaches a critical threshold, and outbreaks occur.

Because this process takes years, by the time the outbreaks begin, the average
age of the un-immunized population has increased. On the other hand, if nobody
is immunized, most people will acquire the virus at a young age, become
naturally immune (or die), and the average age of incidence will be low.

Here's a link to a slideshow that explains the concept in greater detail (I've
started it at a slide that discusses the Greek rubella outbreak, but if you
want the mathematical models, go back to slide 1):

<http://www.pitt.edu/~super1/lecture/lec1181/023.htm>

