The dose should be repeated. If the error was detected on the same clinic day, you can repeat the dose that day. If the error is detected more than one day later and if the expired dose is a live virus vaccine, you must wait at least 28 days 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. An exception to this is for recombinant zoster vaccine (Shingrix, GSK); the repeat dose should be given 4 weeks after the invalid dose, to reduce the risk of side effects caused by the adjuvant used to enhance the effectiveness of this vaccine. If you prefer, you can perform serologic testing to check for immunity for certain vaccinations (e.g., measles, rubella, hepatitis A, diphtheria, varicella, and tetanus).