The logic built into the backend of the evaluated history and forecaster is complex. While a vaccine may fall outside of the standard schedule, there are "absolute minimum/maximum" limits that will still result in a "Valid" evaluation.
The links below bring you to the latest available guidance for routine vaccination shedules. These links are subject to change frequently, but we will do our best to keep them up to date.
Please review the vaccine in question to make sure what you are seeing does not fall into a "Special Situation" scenario.