A fascinating scenario by @cstross got me thinking: https://www.antipope.org/charlie/blog-static/2021/01/covid-on-mars.html
How would a plausible Mars colony in 2070 handle an epidemic? It would be a very densely populated area with closed loop air supply that might have to wait 15 months for the vaccine relief...

But is that really the case?
Vaccines are lightweight, especially if you just supply a liquid dose and a disposable needle. Total 20 grams, perhaps 50 grams with packaging. 10,000 doses fit in 0.5 tons. Put that in an aerobraking capsule with chutes and it might add up to 2 tons.

Small payload on big booster gives a lot of deltaV, enough for an accelerated trip to Mars outside of optimal transfer windows.
2 tons on top of a Centaur SEC stage gives us a mass ratio of 5.9, so deltaV becomes 7.83 km/s (starting in Low Earth Orbit).

That allows travel times as low as 2 months inside the optimal window, or six month trips even +/- 4 months outside the optimal window.

The downside to these trajectories is that the capsule comes screaming in at 15km/s, compared to the usual 6-7 km/s.

Verdict:
It's possible to pay for a high energy accelerated trajectory mission to Mars to deliver urgent, lightweight payloads.
This cost of this mission would be something like $10,000/dose, but that's with an expensive launcher like the Atlas V.