Formula 1 says it will not hold a World Championship race in a country that prevents any team entering as a result of coronavirus restrictions.
F1 managing director Ross Brawn said: "If a team is prevented from entering a country, we can't have a race.
"Not a World Championship race, anyway, because that would be unfair."
Vietnam has imposed a 14-day quarantine period on visitors from Italy, while Bahrain has employed special measures to ensure its race can go ahead.
The Bahrain and Vietnam Grands Prix are scheduled to be the second and third events of a season that starts in Melbourne, Australia on 13-15 March.