Hanoi still reported the highest number of infections on the day with 370 cases, followed by Nghe An with 95 and Vinh Phuc with 91.
The national tally reached 10,707,568.
A total 3,069 COVID-19 patients were given the all clear on May 21, bringing the number of recoveries so far to 9,393,101.
There are 221 patients needing breathing support, while no death was recorded in the past 24 hours. The total fatalities stood at 43,075.
By May 20, the country had injected 219,047,772 doses of COVID-19 vaccines, including 3,385,880 first doses and 19,600 second doses for children from five to under-12 years old.