Not sure what that has to do with foreign aid, but the average median age in Indonesia is 30yo. Only 6.2% of their population lives to see 65. In the USA, about 15% of our pop lives beyond 65.
As people age, the ability to synthesize Vit D becomes impaired. As the kidney ages it loses ability to 'activate' that Vit D. There'd be very little impairment in a healthy 30yo Indonesian. The ability to manufacture melatonin, which has anti-inflammatory properties, is also impaired with age. A 24yo equatorial Indonesian would have a higher melatonin level than a 50yo irish New Yorker in winter. Even so, Indonesia was one of the last to experience outbreaks, but it currently has the highest number of cases in Southeast Asia
Age, medications, environment, speed and method of care, knowledge database to draw upon, all or any could affect mortality to a much larger extent than Vit D levels alone. You'd have to compare similar populations instead of apples and oranges.
My thought is vitamin D levels would be lower on an aged population with less sunlight overall. Surprised to find such a difference near the equator. They compared low levels to high levels and found 10 times less deaths at high levels. Dr. Campbell just reviewed that article and only question he had was on the old school way they reported D3 levels.