When a vegetarian decapitates a cabbage it would, therefore, appear they are slaughtering an aware, interactive being. Every vegetarian has an immune system that exterminates bacteria, viruses, rickettsiae, chlamydia, spirochetes and protozoa. And protozoa may be the simplest single-cell organisms of the animal kingdom but they are animals nonetheless. Oh sure, PETA members may disparage the microbial IQ but these mini-merchants of mortality and morbidity have proved themselves clever adversaries in the battle to cure any number of dread diseases. But blame shifting ill-becomes an advocacy group which aspires to be taken seriously on matters of animal ethics.
Immunosuppressants are readily available by prescription.
If we don't kill animals, malnutrition could make at least some of us vulnerable to a host of ailments, including opportunistic infections. I know, I know. There are nutritionists who argue that plants alone are sufficient to meet our need for high-grade protein, etc. But there are also nutritionists who dispute this claim. And there are large populations of people to whom vegetables, by reason of geography, weather, etc., are not readily available.