The answer is:

d. getting the booster vaccine Tdap.

It's always a good idea to cover your mouth when you cough and also avoid contact with someone who is sick, but this is not always possible. Taking a multivitamin won't protect you from getting Pertussis. The DTaP vaccine is given to babies and children to protect them against Tetanus, Diphtheria and Pertussis but protection can decrease over time. Tdap is a booster vaccine that is given to teen girls and guys.