I am curious, if this is so (“in accordance with the known in instructions of the Rebbe … in all matters of medicine one must do according to the instructions of specialist physicians”), how does that fit with ultrasounds?

Specialist physicians consider ultrasounds a standard part of care, to the extent that many doctors refuse to treat patients who will not have ultrasounds.

However, the Rebbe is known to be against routine use of ultrasound.

Studies have not yet found clear evidence of damage from ultrasound, however we still refuse them, against the advice of specialist physicians, without a compelling reason to do one.

We feel justified because the Rebbe warned against it, and we know that prior to ultrasounds, women were told that it is safe to routinely undergo X-rays of themselves and their babies! (Obviously we now know the dangers of that.)

The Rebbe’s letters regarding vaccination seem to have been in regards to the polio vaccine in particular, and during an ongoing outbreak. Although it is quite logical to extend that to the MMR during a measles outbreak, it is not so clear as to whether that hora’ah can be extended to the full vaccine schedule today.

Either way, it is a stretch to assume that we follow “majority medical advice” automatically, when in fact the Rebbe frequently went against it. The advice of a Rofeh Yedid would seem more appropriate.