What is the difference between the Td (Tetanus) and the Tdap (tetanus, diphtheria and pertussis) vaccines?
The Td vaccine protects you against getting tetanus and diphtheria only. The Tdap vaccine will not only protect you from those two diseases but also from pertussis (whooping cough). As a child, you may have been immunized against pertussis, but that immunity wears off over time, so by the time you enter college, you probably aren’t immune to pertussis any more. Pertussis is a highly contagious respiratory illness that often leads to other more serious illness.