You Do Need power plug adapter while traveling from Saint Lucia 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 Saint Lucia is G. This is how they look like.

Saint Lucia

In Saint Lucia, outlets of type G are in use.

Type G

Vatican City

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

Type C

Type F

Type L