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

Here is Why You Need An Adapter

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

Vatican City

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

Type C

Type F

Type L

Pitcairn Islands

In Pitcairn Islands, outlets of type I are in use.

Type I