Do we need the Hepatitis A vaccine ? Our parents did not get it !
India is classified as "highly endemic" for Hepatitis A virus. That means almost all of the water is contaminated with the virus. So small doses of the virus in our drinking water would stimulate our immune system, produce antibody and confer protection.
Changing lifestyles and imroving sanitation means we drink bottled water or use RO/UVF filtered water in which all organisms including viruses are killed. So we are left unprotected to the virus. Hence the need for the vaccine.