Vietnam’s chart of Covid cases is quite interesting:

There was virtually no Covid in Vietnam for all of 2020, and even the first half of 2021 saw virtually no Covid cases as well.
But then, in late June, Covid cases suddenly started spiking. Cases started falling in September, but then quickly spiked again, to a new high, and remain at peak levels today.
Why did Vietnam have virtually no Covid for over 15 months, and then suddenly start seeing tons of new cases?
For some reason, despite the fact that Vietnam was largely Covid free, the nation began vaccinating its population earlier this year:

Vietnam began rolling out the vaccine shots on March 8, but even as late as July 1, only 0.2% of the nation was fully vaccinated. Today Vietnam is about 57.5% fully vaccinated.
Even as recently as October 1, only 10% of the nation was fully vaccinated.
I am not saying the vaccine is what’s causing the rise in Covid cases in Vietnam.
It’s just odd timing.
A few months ago, I noticed a similar phenomenon in Mongolia, where they had no Covid for over a year, but then suddenly started seeing cases spike out of the blue in late March of this year:

It was right around the time they started rolling out the vaccines in Mongolia:

I don’t know why this is.
But again, it’s very odd timing.
In terms of the vaccines Vietnam uses, they began with AstraZeneca being approved on January 30, then the Russian Sputnik on March 23, and then in early June approved use of China’s Sinopharm vaccine, as well as Pfizer, Moderna and Johnson & Johnson.
The massive spike in cases in Vietnam does seem to coincide with their approval of the Sinopharm vaccine and the 3 American vaccines.
Mongolia has approved Pfizer, AstraZeneca, Sinopharm and Sputnik, although I wasn’t able to find the dates each vaccine was approved. I’m assuming Mongolia used Sinopharm and Sputnik first as Mongolia is sandwiched between China and Russia geographically.
Correlation does not equal causation.
But these charts do raise some questions.