Here are some links that I think can provide you with reliable health information:
http://www.trestlewoodpediatrics.com/
This is the link to the website for my pediatric practice.
http://www.aap.org/
This is the website for the American Academy of Pediatrics.
http://www.healthychildren.org/English/Pages/default.aspx
This website was designed by the AAP as a parenting resource.
http://www.cdc.gov/
This is the Centers for Disease Control and Prevention (CDC) website.
http://www.cdc.gov/vaccines/
The CDC immunization pages.
http://www.chop.edu/service/vaccine-education-center/home.html
The Children's Hospital of Philadelphia website about immunizations. This is a comprehensive resource with detailed information about vaccines.
I will add more links as I find them. Good luck!