TLDR: the economist don’t have any actual data for China or Vietnam, so they used western nations’ excess deaths (primarily due to covid) to model excess deaths due to covid for China and Vietnam.
A method that is totally not scientific or standard or used by the medical profession to do such analysis, but which just ‘conveniently’ produces massively higher ‘excess deaths’ figures for China and Vietnam that totally fits the western party line lies about China and zero covid strategies.
Ironically, this shoddy/purposeful misleading work done by the Economists is actually incredibly interesting and useful, because it gives us an estimate for what covid deaths might have been for China and Vietnam had they followed the western ‘let ‘er rip’ covid ‘strategy’ aka herd immunity.