This kind of warfare [i.e., biological] would have us devouring the world’s children in a manner of speaking and those who are immunologically impaired, presuming we were going to immunize our own population but not those of the antagonist. Thus we would be conducting warfare which by definition would be indiscriminate rather than selective. We would lose control of the evolution of the bacteria that we would be releasing in the multitrillions.
Source: wiktionary