it would prevent infection and transmission as much as any other vaccine would. you're just priming your immune system to handle something its not actually seen before. you can still get the virus, it will still affect you, but your immune system will recognize and deal with it much much faster. thinking logically, if you are given the virus, your body will still make copies for a short amount of time and you would still be able to give it to someone else. getting the vaccine makes the window of opportunity much smaller and dramatically lowers the risk that you will die from it.