Covid-19 outbreaks among the Tigers and Irish squads rendered the fixtures impossible and Premiership Rugby panel chairman Andy Higginson, chief executive Darren Childs and rugby director Phil Winstanley met to decide on the allocation.
Both games will be officially recorded as 0-0 scorelines, but with Newcastle and Bath handed victories while their opponents take half the points, which would typically be awarded for a draw. Newcastle head into the new year in second place as a result, with 16 points.
Leicester had returned what they reported as a "small number" of positive tests after their European Challenge Cup win over Bayonne, but contact tracing meant several more players were forced to isolate ahead of the festive fixture and the training ground was shut down as a precaution.
London Irish did the same after returning positives in their December 21 screening, with further individuals later showing symptoms. Their training ground reopened on Monday.
A Premiership Rugby statement was released on both verdicts, concluding in each case with the following message.
"The health and safety of players, staff, management, officials and supporters is our only priority, so the correct decision was taken to call the game off."