You Do Need power plug adapter while traveling from United States Virgin Islands to Vietnam.

Here is Why You Need An Adapter

The outlet and plug type used in Vietnam are A, B and C and in United States Virgin Islands are A and B. This is how they look like.

United States Virgin Islands

In United States Virgin Islands, outlets of type A and B are in use.

Type A

Type B

Vietnam

In Vietnam, outlets of type A, B and C are in use.

Type A

Type B

Type C