An one-to-one correspondence between two sets exists only if a mapping exists between the two sets such that each element of the first set maps to exactly one element of the second set and each element of the second set maps to exactly one element of the first set.
Everyone needs protection from tetanus. The DTaP vaccine (diphtheria, tetanus, and pertussis) can help prevent tetanus in young children. DTaP shots are recommended for healthy babies at ages 2, 4, and 6 months, and again at 15 through 18 months. A DTaP booster is recommended for children ages 4 through 6 years old.
Get a tetanus booster shot after certain injuries. Usually, the bacterial toxins enter the body through a break in the skin caused by an object contaminated with tetanus. If you have one or more of the following injuries or wounds that are prone to tetanus, you should get a tetanus booster shot.