Hard to say, I only have experience with the naltrexone pills which I'd say to wait 5-7 days for. The shot would probably linger in your system a fair bit longer as that is sort of the point.
Are you sure you want to use the Vicodin? You made the decision to go on the shot at some point and it's difficult to get on it as you have to abstain for 10 days leading up to it. Would you be able to do that again if your use got out of control?
I'm not saying don't do it, that's your decision to make. Just make sure you're weighing up the decision when you make it.