A: The dose should be repeated. If the expired dose is a live virus vaccine, wait at least 4 weeks after the previous (expired) dose was given before repeating it. If the expired dose is not a live vaccine, the dose should be repeated as soon as possible. If you prefer, you can perform serologic testing to check for immunity for certain vaccinations (e.g., measles, mumps, rubella, varicella, and hepatitis A).