What is the exception to not needing to restart a multi-dose vaccine series?

The exception to not needing to restart a multi-dose vaccine series is oral typhoid. When a person does not complete the full multi-dose series of oral typhoid vaccines, it is generally not required to restart the series if a dose was missed. Instead, the individual can simply receive the remaining doses to complete the series. This is due to the unique nature of the oral typhoid vaccine, which is less sensitive to timing compared to other vaccines.

In contrast, vaccines like MMR (measles, mumps, rubella), influenza, and pneumococcal typically have more strict guidelines regarding missed doses. For these vaccines, if the series is interrupted, it is often recommended to restart or continue the series as per the specific guidelines to ensure adequate immunity. Therefore, oral typhoid stands out as the exception in the context of multi-dose vaccine series completion.