It's a relatively new vaccine (from the late '90s) and, in the US, the main reason people get vaccinated is to attend school, so anyone who was able to attend s

It's a relatively new vaccine (from the late '90s) and, in the US, the main reason people get vaccinated is to attend school, so anyone who was able to attend school before the late '90s wouldn't have been vaccinated without going out of their way (perhaps for international travel, which is why I was vaccinated -- in the late '90s). Additionally, hepatitis outbreaks are associated with sanitation problems. Chicken pox, measles, mumps, etc. are associated with putting many people close together, like in a school, so it took a while to add hepatitis to vaccination schedules. It's also true that many people believe the vaccination wouldn't be necessary if we could just get people to pay attention to sanitation, so there is some opposition along the lines of "if we require this vaccine, we're admitting defeat as far as a clean society is concerned."