You Do Need power plug adapter while traveling from Fiji to Vatican City.

Here is Why You Need An Adapter

The outlet and plug type used in Vatican City are C, F and L and in Fiji is I. This is how they look like.

Fiji

In Fiji, outlets of type I are in use.

Type I

Vatican City

In Vatican City, outlets of type C, F and L are in use.

Type C

Type F

Type L