Are you for or against letting your children be immunised against diseases?

Do you think it is wise to have your children vaccinated against diseases such as polio or meningitis? Do you think that it is safe for children who’s immune systems are not as strong as adults’ immune systems to be immunised? Why is this? Is it because there are many cases of the vaccination not working properly? Or is it because the vaccine may be in its first few years and you do not trust its effectiveness yet?