You Do Need power plug adapter while traveling from Samoa 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 Samoa is I. This is how they look like.

Samoa

In Samoa, 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