A vaccine is not effective on someone who is infected (or about to be infected). But it's going to take a long time to have a vaccine because vaccines are administered to healthy people so they must be very safe.

I think it's much more likely that we'll have effective anti-viral and/or clonal antibody treatments long before effective vaccines. There are a half dozen trials ongoing now for various new and existing anti-viral compounds.   Clonal antibody treatments don't even require any research breakthroughs, just the time it takes to isolate and clone cells that produce effective antibodies.

Both anti-virals and antibody treatments are used to treat sick people, so they don't have to be very safe-- they only have to be safer than the virus. If they're highly effective they only need to be slightly safer than the virus.  Because they don't need to be very safe, we don't need to do much testing before widely deploying them.

If we find anti-viral treatments which are highly effective against sars-cov-2 then in the developed world the issue will largely be resolved.  You get symptoms... you visit a doctor and get an anti-viral shot. Done, no need for a disruptive response because people won't die. (The situation in less developed parts of the world might not be quite so good).  In the long run, a vaccine eliminate the issue (hopefully-- for some human coronaviruses immunity doesn't last very long).