Stay away from people that are coughing, just like with anything else, or sneezing. And if you're having symptoms go get it checked out.
This isn't something where we want to scare people at all.
No vaccine is 100 percent effective though we hope it is very effective. We know the vaccine would help so people wouldn't get the complications from mumps if they did get it that, maybe they'd get a milder case if they did get it.
Don't let people sneeze on you, and if you sneeze, sneeze into your elbow.