July 30 week 12 homework check the following link and post impression

http://www.nytimes.com/2008/03/21/us/21vaccine.html?_r=2&oref=slogin&

Some people (or parents) decides not to take vaccination for various reasons.

Maybe because it's economic reason, or maybe their beliefs.

Vaccination itself is not completely risk free.

But in order to protect public welfare, government promotes vaccination.

It's like the tradeoff between individual decision and public welfare.