Rav Dovid Karliner (Sde Chemed Kuntres Metziza 3:4): …It remains for us to explain how to decide in a matter that doctors based on their knowledge and experiments decide against the Tradition of Chazal. I have already explained in Sheilas Dovid when there is a tradition of Chazal which is undisputed and it is from Sinai in a halachic matter such a treifos. However regarding the condition of an animal which our tradition doesn’t deem a treifah, it can certainly be curable and it doesn’t concern us if the doctors decide based upon their studies that it is incurable. We rely on the Talmudic Sages and their Tradition and we don’t agree with the view of the doctors that nature has changed since this is a matter which is relevant to halacha concerning such things as treifos… we don’t say that nature has changed. Because if it were so then we would have been informed that a time would come that nature changed and these animals would be prohibited by means of this illness or this physical deficit. But from the fact that our Talmudic Sages did not agree in certain cases that indicates that they did not have a clear tradition or they are disagreeing what the majority case is but nevertheless they agree with each other that at least a minority exists. Therefore since there is not a clear tradition and there isn’t a direct halachic consequence but it only has consequences regarding certain fact than we can say that it is possible that nature has changed over time. In contrast where there is a clear tradition and the Sages are in agreement with each other than nature will never change and we don’t listen to the contrary view of the doctors. All this is only relevant regarding halachic issues. However regarding conditions that Chazal consider dangerous to health – the correctness of these statement can change over time…It is also possible that in their times there was no cure for a particular condition but now a cure has been found for something which Chazal don’t claim is a Tradition from Sinai but rather they knew from the medicine of their day. In fact it is possible that they learned many things from the doctors of their time such as scurvy (Yoma 84a) which R’ Yochanon learned how to cure from a non-Jewish woman. Nevertheless he poskened that it was allowed to profane Shabbos for the sake of this cure even though it apparently involved transgressing a Torah prohibition. There were also many cures that Chazal described as being learned from “a certain Arab” and other secular sources. Thus so while it is true that many cures were known to Chazal from Divine Inspiration (Sod HaShem) but it is not possible to say that all of their cures were such. Therefore when Chazal said about certain medical treatments that Shabbos can be violated for them in their times and places it was because they didn’t know any alternatives and they considered the medical conditions to be dangerous and thus it was permitted to profane Shabbos for them. But once it has been determined through medical science that these conditions are not dangerous we cannot profane Shabbos for them…. As long as all doctors are in total agreement then the condition is not considered dangerous anymore. However if there is not universal agreement then it is possible to say there is a possibility of error and the assumption of danger remains…. In my opinion concerning all the dangers and cures that require transgressing Shabbos mentioned in the Talmud, if there is not universal agreement of the doctors then we follow the view in the Talmud even to transgress Shabbos. But when there is universal agreement that in modern times there is no longer danger then we say that nature has changed in this matter…
Rav Sherira Gaon (Otzair HaGaonim - Gittin 68b page 152): Our Sages were not doctors and what they said is merely a reflection of what was known by the medical experts of their times and therefore there is no mitzva to accept their statements concerning medicine….
Moreh Nevuchim (03:14): Don’t expect from me to show that everything that our Sages said regarding astronomy in fact agrees with observation. That is because mathematics was not fully developed in those days and their knowledge was not based on information received from the Prophets. Rather it was based on their own personal knowledge as experts or it was taken from the astronomers of those times. However I am not going to say that what they say that in fact agrees with observation is incorrect or was accidentally true. Rather whenever it is possible to explain a person’s words as being in accord with observation, it is the duty of every educated and just man to so.