Well, its simply really. If your not vaccianted yet, you will develop a higher risk of getting effected by the virus your trying to prevent. However, people who are vaccinated are safe and are less likely to develop harsh symptoms but can still get the virus, all though the symptoms will be minor.
Contraceptives are also known as birth control which are used to prevent sperm from the male body getting to the eggs from the female body. You would likely consider the side affects and effectiveness when using contraceptives.