In its announcement Wednesday it said further if the first shot was a AstraZeneca vaccine, the second could be a Pfizer or Moderna shot.
Both Moderna and Pfizer utilize mRNA to elicit an immune response.
Due to a shortage, several countries have looked into mixing Covid vaccines.
Vietnam first allowed AstraZeneca and Pfizer vaccines to be mixed in July.
Ho Chi Minh City, epicenter of the fourth coronavirus wave, has let many people who first got a Moderna vaccine to switch to Pfizer as the supply of the former has run out.
Vietnam has vaccinated over 23.5 million people, with 3.7 million getting two shots.