First mistake people make is assuming a vaccine will be 100% effective in 100% of the population. Second is overlooking the difference in usage: the US will need over 300 million doses of vaccine, but only around 60 million doses of LLmab. Everyone would need a vaccine (no idea who would have an infection that would be dangerous) but only the 20% who have complications would need LLmab.

And there's no vaccine for HIV, influenza, or cancer.