Vaccine Series Completion Guidelines

Core Principles

The Advisory Committee on Immunization Practices (ACIP) recommends that there is no need to restart a vaccine series regardless of the time that has elapsed between doses, applying universally across all vaccine types, including those requiring multiple doses like Shingrix 1, 2, 3
The fundamental guideline principle is clear: a vaccine series does not need to be restarted, regardless of the time elapsed between doses and regardless of vaccine type, as consistently reinforced by the ACIP 1, 2, 3

The American Academy of Pediatrics, as reflected in the journal Pediatrics, suggests that the initial dose of a vaccine series counts toward completion of the series, and the second dose should be administered at the patient's next available appointment, without repeating the first dose 1, 2, 3
Administering the second dose of Shingrix at the patient's next available appointment, without restarting the series, is recommended by the ACIP, as the initial dose from a previous time counts toward completion of the series 1, 2, 3

The Centers for Disease Control and Prevention (CDC), through the Advisory Committee on Immunization Practices (ACIP), advises against restarting the vaccine series simply because of a prolonged interval, as this would unnecessarily expose the patient to additional doses, increase costs, and delay completion of protection 1, 2, 3