I think it's very difficult to give you a number of months or years.
I'll give you two examples. HIV has been there for 35 years. We have excellent antivirals, molecules, but no vaccine. The virus is more complicated. There will be a vaccine maybe sometime, but it is difficult. Hepatitis B had a very early vaccine with an attenuated virus and then a recombinant vaccine, which has now been used for decades. Somewhere in between these two it will be.
Now the issue is testing, and Volker Gerdts is the most competent here to answer. You need to test controlled cohorts during the course of an infection, and that takes time. Even antiviral clinical trials can be faster than clinical trials for the vaccine.
There you have hepatitis B and HIV, and we're somewhere in the middle. Predictions are very hard to make.