They guess at which flu strains will be active each year. When they guess correctly, the vaccine is pretty effective. When they guess incorrectly, the vaccine doesn't do anything against flu strains it wasn't designed to work against.

Here's the difference:

This vaccine will be designed specifically against this virus.
It will work well against THIS virus, or it won't be approved.

That's a year to 18 months from now.
That's why we need treatments NOW.

I wish people would stop making flu/Covid-19 comparisons. They are simply not valid.

Remdesivir is likely a better hope than chloroquine, since it was designed to work against Ebola but they are saying that it actually looks like it would be a better fit against COVID-19