If we go by theories by their earliest incarnations, "germ theory" rejected that diseases could be caused by deficiency in micronutrients. "Terrain theory" arguably was the closest to the truth on those.

Also, by the standards of so-called "evidence based medicine" where we care less about the proposed mechanism a treatment works by, and more about whether it actually works, then miasma theory (or maybe it's more accurate to call it miasma practice, then?) doesn't look so bad. Florence Nightingale didn't bury horses because she believed in germ theory, she did it because they stank - and because she had developed statistical evidence that such hygiene interventions worked, whatever the mechanism. It took a long time for germ theory to get sophisticated enough that we can say it started saving more lives than sanitation (which was developed based on miasma theory).

The first incarnations of an ultimately correct theory often work worse in practice at the start.

Not that it excuses Kennedy.