I'm not against the concept of vaccines. In on themselves, they can be a very useful tool to cure and prevent diseases, when not being used for DS fuckery, just like airplanes are incredible means of transportation, but can also be terrible tools of destruction when used in bombing raids.
Of course, never undergo any medical procedure or take any drug without first doing some research and questioning a trustworthy medical professional about it first.
The problem is that even if a vaxx is technically safe, a lack of quality control in manufacturing, or a lack of care in handling/transportation, can render it dangerous, if not lethal.
In addition, a mistake in application (gets into the blood stream) or wrong temperature can render it dangerous.