No matter which side of the debate you're on, I think we can agree giving a child nine vaccines at once is probably not the best idea. We've spread out my sons vaccines so he receives all the recommended ones but a few weeks apart.
(Occasionally, overwhelming logic will suffice. E.g., sure, I agree that there is no need for a clinical trial on parachutes for those jumping out of airplanes.)
My exception for "overwhelming logic" was intended to stave off the trivial responses like, "Oh, so you think we should have clinical trials for parachutes."
Surely, if enough agree with you, however, then we will consider there to be "clinical equipoise" and trials will be done.
With regards to "barbaric" medical practice, you seem to be conflating pre-scientific medicine with scientific medicine. "Experts" in ritualistic pre-scientific medicine probably knew no more about disease than did the completely uninformed. They were not "experts" in any meaningful sense. And, indeed, had someone been around practicing evidence-based medicine at that time, they could have completely changed the world.
As much fun as it is to talk philosophically about this, there are actually plenty of people who have wondered about vaccine administration. From my reading of the articles, the evidence does not show meaningful adverse effects from the practice of multiple vaccination. I'd encourage you to do your own reading on the topic.
Firstly, no I'm not. Secondly, you seem to believe scientific medicine is effectively infallible. Nearly every day a new study indicates studies performed just a year or two or ten ago are inaccurate. Indeed, that is the very nature of science.
What we're discussing here is logic. It is not logical to accept the opinion of a medical expert, particularly without trials. This is precisely why most people will undertake the logical next step and seek a second opinion. Ultimately, certainty is impossible but blind acceptance is rarely ever wise and always illogical.
The fact that there is turnover in medical knowledge does not mean that your personal preference carries the same weight as evidence or even expert consensus.
Isn't it LOGICAL that the immune system will react more rigorously when presented with more strains of diseases, increasing immunity to each of them?
You don't answer questions like this based on common sense!
However, I do know that activation of the immune system is costly to an individual organism. It uses energy, and this can lead to sub-optimal functioning of other systems.
I do not know if giving multiple vaccines at once means that activation of the immune system is greater, but it would seem logical that a larger number of foreign particles in the bloodstream would do that.