Harlequins and Saracens have had a second Premier 15s fixture in a row postponed because of coronavirus.
Quins top the table, with Sarries second, but could not play Saturday's match against Wasps because of "ongoing Covid-19 concerns" at the club.
The postponement of Saracens v Sale was announced less than four hours before kick-off on Saturday.
The Rugby Football Union said the decision was because of the major incident declared in London on Friday.
Sarries' game was due to be played in north-west London a day after the city's mayor Sadiq Khan said the spread of Covid was "out of control".
Last weekend's match between Harlequins and Saracens was also postponed after one Quins player tested positive for Covid-19 with several other players and staff isolating as close contacts.
There is no coronavirus testing in Premier 15s and on Tuesday the RFU's head of women's performance Nicky Ponsford said the organisation was as "confident as it can be" that the season would be completed.