That is not the relevant question in this case. As I said, the question that matters is do vaccines, for COVID, influenza, hepatitis, among others, increase the odds of survival? If yes, compare that to the risk of the vaccine. Compare them. If expected benefit > risk, then vaccine. That's the decision making tree and it's very simple.
The difference is treating A for cancer with chemo does not by necessity mean B and C and DDD and ZZZ do not get chemo. There is no 'list' for chemo, so no need to prioritize Patient A over B because A's odds are lower of dying. A, and B and C and DDD and ZZZ can all get treated simultaneously, starting tomorrow.
The cost is relevant but only to the insurance company, and/or the patient. Transplant decisions aren't really about cost, but about the transplant system's moral and ethical and medical duty in the face of far more patients who need transplants than available organs to prioritize patients with the best chance of success, which by definition is to deny treatment to EVERYONE ELSE ON THE LIST for that particular organ, the heart in this case.
You can't define "significantly increase" or provide evidence vaccines wouldn't meet this vague bar. And, yeah, in a pandemic involving a novel disease, we're all required to make decisions based on the best information we have available, because we cannot wait to decide until long term data are available.