Greater Anglia is cutting some of its services from Monday as the Omicron variant of Covid has led to a sharp fall in passenger numbers - especially among commuters.
Most trains will continue to operate but a small number of services on most lines - including the main route from Ipswich and Norwich to London - are being withdrawn.
The company also fears staff shortages as employees start to call in sick. Full details of the withdrawn services can be found on Greater Anglia's website.
A statement by the company said: "This is due to falling passenger numbers as people follow advice to work from home. We also have to plan for our staff being affected by the Omicron variant, especially as we’re already starting to see the early signs of its impact, to ensure we can continue to provide a reliable service."
After Boris Johnson went on television last Sunday to tell people to get jabbed and work from home if possible, the number of people travelling by Greater Anglia trains, especially on commuter services, dipped significantly.
Passenger numbers fell to about 50-55% of pre-pandemic figures, similar to those seen in July. The fall was largely driven by a fall in commuters - leisure travel remained at its previous level, possibly as some people made early trips home to Christmas.
However there were anecdotal reports from rail staff and passengers that the number of travellers fell really significantly in the second half of the week after government Chief Medical Officer Prof Chris Whitty urged people to minimise social contacts in the run-up to Christmas.
Greater Anglia, like all other rail companies, is maintaining a high level of cleaning on all its trains and passengers now have to wear face coverings unless they have a medical exemption.
This week the number of passengers expected to travel is uncertain because it is not known how many people will be travelling across the country to join families at Christmas - but the last-minute rush to do shopping in city centres is expected to be much less than expected a few weeks ago.
Train services in the region are running fairly normally over the Christmas period except for the two bank holidays December 27 and 28 when buses replace trains between Colchester and Shenfield because a bridge is being replaced near Chelmsford.
There are no services on Christmas Day or Boxing Day except a few between London and Stansted Airport on December 26.
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