Vaccine does not mean cure. We did not have a Covid cure either. And much like the covid vaccine isn’t 100% effective, neither is this. However, it is proving effective, especially in combination with other drugs and at certain stages of treatment.
Stage 4 clinical trials were concluded in Cuba in 2017. Stage 2 trials were concluded in the US in 2023. I believe, strongly, that the embargo has increased the amount of time the research has taken - cooperation is impossible during an embargo.
Even if they lift the embargo tomorrow the drug wouldn’t come on the market, however it is because of the embargo that the use in treatment has taken far, far longer than it would have otherwise.
Edit: I admit I knew less about the vaccine than I thought I did (edited my comment to reflect what I have learnt)