Reductions of 31% and 42% were recorded in Derry City's two postal areas.
The number of new Covid-19 cases recorded over the last week in County Derry has fallen by over a quarter on the previous week's figure.
1,004 cases were identified in the county last week, with drops of 30.7% and 42.2% being recorded in Derry City's BT47 and BT48 postal areas.
The decrease represents a fall of 28.5% overall on the previous week's figure, with the number dropping everywhere except for Magherafelt (BT45), which recorded one more case than last week.
Derry's rate per 100,000 of population has subsequently taken a dip to 404.7 and is now below the overall NI figure of 437.1 for the first time since July 20.
Locally, the highest rate (580.3) was recorded in Limavady's BT49 postal area, while Portstewart (BT55) had the lowest at 255.8.
There are no County Derry postcodes in the top ten rates per 100,000 in Northern Ireland.
The percentage of people testing positive for the virus has also fallen to 7.8%, despite the number of tests also decreasing by 25.5% in the same period.
Despite the reduction in cases and rates, a further 18 Covid-related deaths were recorded over the last seven days in the county's three local government districts.
The highest number (8) were recorded in Causeway Coast and Glens, while there were four deaths in Derry City and Strabane and six in Mid Ulster.
A further fall in inpatients being treated for Covid-19 in the area's hospitals was also recorded, with 74 Covid patients now in hospital across Altnagelvin, Antrim Area and Causeway hospitals.
The uptake in vaccine rates has slowed in recent weeks, with 69% (1,305,556) having received one dose and 1,201,074 (63%) having had both doses.
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