You Do Need power plug adapter while traveling from American Samoa to Vanuatu.

Here is Why You Need An Adapter

The outlet and plug type used in Vanuatu is I and in American Samoa are A, B, F and I. This is how they look like.

American Samoa

In American Samoa, outlets of type A, B, F and I are in use.

Type A

Type B

Type F

Type I

Vanuatu

In Vanuatu, outlets of type I are in use.

Type I