"Question: Is a third or fourth year medical student considered a full-fledged physician for halachic purposes?
Answer: A medical student has the same halachic coverage as a house staff physician or attending physician.
Comment: Although the student has no legal responsibility for patient care, and although he may not have adequate knowledge to exercise mature medical judgment, his aid is often necessary and nearly always beneficial. Time is saved by the senior physician because additional hands are available. The halacha does not distinguish between medical student, clinical clerk, resident, and attending physician, or even layman, insofar as all contribute to the total patient care. The obligation to aid a dangerously ill patient falls not only on the graduate physician but on anyone able to and asked to render assistance. Included in this obligation are first- and second-year medical students and certainly third- and fourth-year students who possess considerable medical knowledge and are essential members of the diagnostic and therapeutic team... [A] medical student has the same halachic coverage as the graduate physician, including laws pertaining to the Sabbath and Yom Tov."
From: "Practical Medical Halachah" by Dr. Fred Rosner and Rabbi Moshe D. Tendler, 1997, page 15.