Really even assuming an utter breakdown in norms for not using chemical weaponry they would lose that arms race as the adversary would only need one non-immune

Really even assuming an utter breakdown in norms for not using chemical weaponry they would lose that arms race as the adversary would only need one non-immune chemical weapons. Of course the implications of the gene mods go far beyond that niche military application. Being able to reliably mod organs is obviously therapeutically helpful - say being able to reverse sickle cell anemia. Being able to "vaccinate" against toxins is likewise obviously helpful. Drugs that technically work on the pathogen but would be lethal to the patient could be used harmlessly if the patient was made resistant first.