[gota]

I just read this, posting the reference in another reply, seems to be a good enough summary:

"One of the reasons Vietnam was able to act so quickly and keep the case count so low is that the country experienced a severe acute respiratory syndrome (SARS) epidemic in 2003 and human cases of avian influenza between 2004 and 2010. As a result, Vietnam had both the experience and infrastructure to take appropriate action. Vietnam makes many key containment decisions in a matter of days, which may take weeks for governments in other countries to make. Although Vietnam is a highly centralized country, a number of key decisions were made at the local level, which also contributed to the swift response."

https://ourworldindata.org/covid-exemplar-vietnam