Passive	Active
MEANS OF ACQUISITION	Receiving preformed antibodies	Exposure to foreign antigens
ONSET	Rapid	Slow
DURATION	Short span of antibodies (half-life = 3 weeks)	Long-lasting protection (memory)
EXAMPLES	IgA in breast milk, maternal IgG crossing placenta, antitoxin, humanized monoclonal antibody	Natural infection, vaccines, toxoid
NOTES	After exposure to Tetanus toxin, Botulinum toxin, HBV, Varicella, Rabies virus, or diphtheria toxin, unvaccinated patients are given preformed antibodies (passive)—“To Be Healed Very RapiDly”	Combined passive and active immunizations can be given for hepatitis B or rabies exposure