Which vaccine is administered as a single dose?

The adenovirus vaccine is administered as a single dose, making it unique among the options provided. In the context of vaccination schedules, the adenovirus vaccine is designed for military personnel to protect against respiratory illness caused by adenovirus types 4 and 7. Its administration as a single dose is particularly beneficial in military settings where prompt immunity is necessary for operational readiness.

In contrast, the other vaccines listed typically require multiple doses or booster shots to achieve optimal immunity. For example, the influenza vaccine is usually administered annually due to the evolving nature of the virus, while the measles, mumps, and rubella (MMR) vaccine usually involves two doses to ensure full protection. The anthrax vaccine, which is given to certain military personnel and at-risk individuals, also requires a series of doses for complete vaccination. Understanding the specifics of each vaccine's administration schedule helps in recognizing the significance of the adenovirus vaccine's single-dose regimen.