Which vaccine has a booster interval of N/A?

The correct answer is the Varicella vaccine, which stands out because it does not require a booster dose for individuals who have received the complete primary vaccination series. In most cases, individuals who receive the two-dose schedule of the Varicella vaccine are considered protected for life, meaning that there is no established interval for a booster dose.

In contrast, other vaccines listed typically have recommended booster intervals due to the waning immunity that occurs over time. For instance, Diphtheria and Tetanus vaccines do require booster shots every 10 years to maintain immunity. Typhoid (Injectable) has a recommendation for booster doses every two years for adults at risk or traveling to endemic areas. Yellow Fever vaccination requires a booster primarily for those at risk who received the initial vaccine more than 10 years ago. Therefore, Varicella is unique in its lack of a standard booster interval requirement for continued immunity.