However, some changes to operations could come as early as Monday.
It came as ScotRail axed or truncated six services on the Glasgow-Stranraer line from today.
The operator said passenger numbers had reduced from 15 per cent to 10 per cent of normal across its network following the start of the new mainland Scotland lockdown on Tuesday.
They had fallen as low as 5 per cent at the start of the pandemic crisis last March.
The number of ScotRail trains running has already been reduced to 81 per cent of normal but more reductions are planned because of the sheer number of empty seats on the services still operating.
This is despite ScotRail already cutting more trains than many other operators.
The lockdown has banned all but essential travel, including between council areas.
Analysis by The Scotsman has revealed Scottish taxpayer support for ScotRail and Caledonian Sleeper – the two franchises controlled by Transport Scotland – has doubled in 2020-21 to nearly £1 billion.
ScotRail said its latest reductions, on the Stranraer line, were “due to the impact of Covid on staff availability”.
The number of its staff testing positive for Covid-19 or being forced to self isolate because of contact with colleagues with the virus is understood to have increased over the last week.
ScotRail said: “From Saturday, Jan 9, a number of trains between Ayr, Girvan and Stranraer will no longer run from Monday to Saturday.
"Please check your journey on our app or at scotrail.co.uk before travelling.
“Trains starting from Ayr instead of Girvan/Stranraer:
0653 Girvan - Kilmarnock
1903 Stranraer - Kilmarnock
“Trains terminating at Ayr instead of Girvan/Stranraer:
1809 Glasgow - Stranraer
2108 Kilmarnock - Girvan
“We'll also withdraw the 0612 Ayr - Girvan & 2203 Girvan - Ayr service."
ScotRail halved the frequency of its flagship Edinburgh-Glasgow main line service to half hourly in November as the first stage of a 10 percentage point reduction in trains across the country.
LNER, which runs trains between Scotland and London via the east coast, said “Any reduction in the timetable as a result of the latest measures introduced by the UK and Scottish governments is under review.”