In the given options, the task is to identify the mis-spelt word. Let's examine each option:
- Vaccinate: This word is correctly spelt. It refers to the act of administering a vaccine to provide immunity against diseases.
- Vacillate: This word is also correctly spelt in this context. It means to waver between different opinions or actions; to be indecisive.
- Vacuum: This is correctly spelt. It denotes a space devoid of matter, or a device used for cleaning floors and other surfaces.
- Varnish: This is also correctly spelt, referring to a liquid applied to surfaces to create a hard, shiny finish.
On examining the options more thoroughly, it initially seemed that "Vacillate" was meant to be incorrect due to the context confusion. However, double-checking reveals no actual spelling error among the provided options.