Sale Sharks' final Premiership match against Worcester Warriors has been postponed to Wednesday after the club reported a number of Covid-19 positive tests, while Gloucester's game against Northampton has been cancelled.
Sharks had initially said that Sunday's match would go ahead while Warriors, who said all their tests were negative, released a contrasting statement that the match was "still the subject of discussions" before the Premiership stepped in.
The Premiership carried out an "urgent review" and a contact tracing program along with Public Health England and the local health authorities before deciding to postpone the match until Wednesday.
Meanwhile, a number of Northampton players are self-isolating following their match against Sale last Tuesday, leaving them with an insufficient number of front-row players to fulfil their fixture with Gloucester.
In line with regulations, Gloucester have been awarded a 20-0 victory and five league points.
Darren Childs, Premiership Rugby's chief executive, said: "When we embarked on Rugby Restart back in August we said from the outset that the health and safety of everyone involved with Premiership Rugby was our priority.
"We completed eight of the nine rounds of Gallagher Premiership Rugby without losing a match so it is with great regret that we make this announcement today.
"We understand and fully sympathise with Northampton Saints' position. They are in this position due to no fault of their own, but unfortunately they cannot fulfil the fixture."
While Gloucester and Northampton are both out of playoff contention, Sale sit fourth in the standings and forfeiting their game could have seen them lose out on a top-four spot, with fifth-placed Bristol Bears also on 64 points ahead of their final match against the London Irish.
Childs added that Sale's match would only go ahead after an additional round of testing on Tuesday and both teams will not be allowed to register new players with the Rugby Football Union prior to the game.