If you test positive for COVID

[KevinJ]

Obviously you cant cruise. You'll get some sort of refund. However I'm wondering if you could apply that refund to another cruise (that was already booked with double points)  to upgrade you cabin class, would you still get the double points? Like paying to upgrade from a balcony to some sort of suite.

[twangster]

Testing positive and using any credit from that towards an upgrade has no bearing on eligibility for double points.

The double points promo will look at the cruise booking and the date it became a confirmed booking to see if a booking qualifies for double points.  Then it looks at the "booked category" such as studio, interior, oceanview, balcony, suite, etc.   It doesn't look into how payments were made to satisfy the overall cost of the cruise. 

Upgrading a booking from a non-suite to a suite (without using RoyalUp) isn't tied to a payment type.  When you upgrade a booking two things must occur.  The cabin category changes to reflect the new "booked category" is now a suite and then you pay any additional amount due because you upgraded.  Payment of the new balance doesn't have to occur until final payment due date if you ask to be upgraded before final payment, or if you ask to be upgraded after final payment then a payment is due immediately to cover the cost of the upgrade.  However payment occurs, a new FCC is applied, a new credit card payment is made, etc. it has no bearing on the booking eligibility for double points.

RoyalUp is the only upgrade method that doesn't provide more points for upgrading cabins.  If booked a balcony and use RoyalUp to move into a suite your "booked category" is still a balcony while your "sailed category" is a suite.  The double points promo will use the "booked category" of balcony for the basis of double points if the date of the booking makes it eligible for double points.