Train services between Leamington Spa, Nuneaton and Coventry have been suspended indefinitelyWest Midlands Trains said staff shortages meant it was unable to provide services until further notice.
It comes after hundreds of trains were cancelled in the run-up to Christmas as rising numbers of railway staff fell ill with Covid-19.
A replacement bus service will be in operation in Warwickshire and with the situation under "close review".
West Midlands Trains said the pandemic had "a significant impact on our workforce" with "more of our colleagues are having to self-isolate".
The operator has been struggling to staff services on its other routes for months due to a shortage of drivers.
Its services between Worcestershire and Birmingham have been subjected to regular cancellation as it struggles to recruit and train new drivers.
West Midlands Trains previously said it anticipated these problems to last until summer 2022.
With regards to its services between Leamington Spa, Nuneaton and Coventry, the firm said its intention was to reinstate "the full timetable on this line as soon as possible".