Bernie Sanders health plan would make coronavirus vaccine (and treatment) free.

The difference in cost to a hypothetical uninsured (the term thats used may be "self-insured") patient could easily be many tens or quite likely even hundreds of thousands of dollars- given the cost of an intensive care bed. Also, Bernie Sanders plan, which we could possibly expedite by declaring a state of emergency to the WTO, and pulling out, saving us a multi-year battle in the WTO, Single payer would insure that patients would receive care based on medical necessity and not be denied care because they had inadequate insurance as many are today (generally, I am not talking about coronavirus)

Note, if somebody is sick with a life threatening illness, they should get care, and worry about the bills later.

In the US, people whose incomes are below the poverty line/destitute may be eligible for emergency medicaid, to pay for coronavirus, especially if they are parents of infant or school age children. At this early stage of the epidemic (here in the US) I really doubt if they would deny treatment even if somebody was uninsured and ineligible for Medicaid,  they would likely just bill and then go after somebody's assets (like a home) if they didn't work out a payment plan.

Other illnesses, that didnt represent a treat like this, I don't know, I would assume quite possibly not, as Trump had to make a special announcement for it.

Note that Medicaid is not insurance, its my understanding that it may seek reimbursement from patients or seize any property they have when they die, if they have not been paid back, even decades into the future*.

*The US is strongly against public health care in its trade policy, and it wants to make it clear and unambiguous that healthcare is not free, ever. Single payer makes a lot of sense and has been proven to work to reduce costs a lot but in a very real sense that ends up making it anathema to the various industries that right now are making a real killing.

(So if Bernie is nominated and become President it would likely lead to a 180 degree turnabout of the US from a country that has, for at least four decades, sook to maximize the profitability of for -profit healthcare, even during tragic epidemics like the HIV disaster when at least 10 million poor people died due to not being able to afford two drugs that it turned out cost pennies to make.

If we were to magically transform thanks to bernie, into a country that views healthcare as a human right(!) right before a major epidemic that promised to represent a huge potential profit opportunity, even larger than the one with HIV (hardly anybody bought these medicines at their $15,000 a year for life in the developing world, though, they just died. )

Bernie's approach is very very far from historic US policy.

that's about as large a turnaround as one could ever imagine.