New figures show that 1,218 staff who work for the trust - which runs the Princess Royal Hospital in Haywards Heath, as well as Worthing Hospital and St Richard’s in Chichester - were absent from work in the week of December 13-19.
That is an increase of 6.57 per cent on the previous week.
However, latest figures also show that the proportion of ambulances queueing outside local hospital A&Es is down from the previous week.
The figures show that 18.37 per cent of ambulances in the University Hospitals Sussex Trust area faced handover delays of more than 30 minutes in the week of December 13-19, compared with 18.52 per cent the previous week.
NHS national medical director Professor Stephen Powis said: “The NHS is on a war footing and staff are taking the fight to Omicron, by boosting hundreds of thousands of people each day, treating thousands of seriously ill Covid patients and delivering urgent care for other conditions, all while seeing a worrying, high and rising increase in absence due to covid.
“We are once again ramping up to deal with the rise in Covid infections, and quite rightly staff are making every possible preparation for the uncertain challenges of Omicron, including recruiting thousands of nurses and reservists, but while we’ll leave no stone unturned to get the NHS battle ready, it remains the case that the best way to protect yourself and others is to follow guidance and to come forward and get your first, second and booster jabs.”