“Could be genetic resistance peculiar to Vietnamese.”
Easier explanation is that it was to be expected because of 16 patients, one death is 6.25% which is higher than the death rate.
With a mortality rate of 2.1%, one would expect no deaths in 16 cases about 71% of the time, so if you believe the published mortality rates, this is plausible.
China has an older population, and most men are smokers, so the fatality rate among men over 60 in China may be quite high.