Any temperature reading outside the recommended range for vaccine storage is a temperature excursion. However, it is generally the total amount of time, or cumulative time, out of range that affects the viability of vaccine. Any time appropriate vaccine storage temperatures are in question, stop giving vaccinations and contact your state immunization program and/or the vaccine manufacturer for further guidance about whether or not a vaccine may be used. The CDC Storage and Handling Toolkit contains detailed guidance on the management of a temperature excursion. See www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf, pages 12–15. Additional information for COVID-19 and mpox vaccine temperature excursions is available in the addendum at the end of the toolkit.