so they wont get sick.
they do not wish to feel the way that they do when the get sick.
many don't enjoy being sick.
People are immunised to prevent the spreading of disease
cough cold
cough cold
Immunization is when your body is protected from a virus or disorder. It usually comes in the form of a shot or inoculation.
If you have active pulmonary TB you are infectious and you must not have close contact with people who are not immunised. If you have previously had TB but it is not active, then you are not infectious and you can do everything normally. Your doctor can tell you which sort of TB you have
If most people over 12 are immunised then younger children would be protected by herd immunity, i.e. there are less people they could catch it from.
Hepatitis B and Hepatitis A.
Reduced likelihood of catching the disease for which the immunisation was given, and if infected a reduced severity of infection. Immunisation also protects the community (those not immunised) when a certain proportion of the populace is immunised because the disease can not get traction for transmission in the populace.
vaccination
It means that you are immunised against that disease
check the cdc website or use a search engine and type "Vaccine information sheets"
If you are 110% guaranteed to refrain from sex, there is no need to get immunised. If you may or will become active, get the shot.