Comment Re:One sided (Score 4, Informative) 858
Assuming you really want to know and aren't just asking to start an argument: It is because newborns are at greatest medical risk if infected by one of the many diseases for which they are vaccinated and because for some diseases (such as Hep B), once it is contracted it can be a lifelong illness which later vaccination cannot prevent/cure. From the WHO:
"Young children who become infected with the hepatitis B virus are the most likely to develop chronic infections:
90% of infants infected during the first year of life develop chronic infections;
30–50% of children infected between one to four years of age develop chronic infections."
"Young children who become infected with the hepatitis B virus are the most likely to develop chronic infections:
90% of infants infected during the first year of life develop chronic infections;
30–50% of children infected between one to four years of age develop chronic infections."