Lockdowns are not about islands. It helps, kinda, but not completely. Vietnam completely sacrificed the tourist industry, unlike US or Europe. Quarantine is at a designated facility, not at home, unchecked, like in US or Europe. And dissent is suppressed.
The last part is a bit unfortunate, but the former ones are really just a matter of decision. And it works.
That said, I want people from island countries to stop saying "being an island country has nothing to do with it", when all evidence and logic says being an island country has a lot to do with it.
I'll happily take criticism from Vietnam, even if I think it's of questionable utility to say "you just did it wrong" when the overwhelming majority of countries seem to have "done it wrong"
And islands still have to watch for random boats from any direction. Right now in Vietnam there is a little outbreak where a group of Vietnamese nationals illegally crossed the border by a fishing boat from Cambodia to Phu Quoc island, trying to avoid the mandatory two-week quarantine. Then they boarded a plane, arrived at their homeland and tested positive. Immediately their steps were traced by police, whole Phu Quoc is under a mask mandate, 3 levels of contacts are tested and in quarantine. It really isn't about being an island. That's a myth, you've been lied to. If you want an example closer to your home, look how hard it is to seal a land border with Mexico. They actually cross by rivers, so water makes it easier.
Lockdowns and people immediately willing be a part of the contract tracing part.
https://www.businessinsider.com/vietnam-coronavirus-measures...