Vaccinations are very much like a blacklist (or signature-based anti-virus). They are generally highly effective against what's on the list, but they don't interact with stuff that isn't on it. Of course, some vaccines work better than others. Additionally, most vaccinations, and all the common ones, are very safe. So even though e.g. the flu shot is not 100 % effective in preventing the flu², it is practically 100 % safe, which means your expected outcome can only improve by taking it.

² I believe the actual numbers are something like 80 % for the flu: people vaccinated against flu strain X only contract it at 20 % the rate of unvaccinated people, or numbers to that effect