WordNet sense 1 (remedy that prevents or slows the course of an illness or disease):

preventative, preventive

WordNet sense 2 (contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse):

condom, rubber, safe, safety

WordNet sense 3 (capable of preventing conception or impregnation):

contraceptive, antifertility

WordNet sense 4 (tending to ward off):

cautionary

WordNet sense 5 (intended or adapted to afford protection of some kind):

protective

WordNet sense 6 (conducive to good health of body or mind):

healthful