LONDON (Reuters) – The number of contacts of positive COVID-19 cases reached by England’s test and trace system in its first two weeks of operation was 87,639, Britain’s health ministry said on Thursday.

The government’s test and trace system is seen as key to helping to monitor the spread of the new coronavirus and ease lockdown measures.

It has been defended as “fit for purpose” by program leader Dido Harding, though she has conceded it is not completely perfect.

The Department of Health said 5,949 people who tested positive for coronavirus (COVID-19) had their case transferred to the contact tracing system in its second week of operation.

It said that 44,895 contacts were identified. Of those identified in the second week, 40,690 people, or 90.6%, were reached and advised to self-isolate.

The previous week’s figures were revised higher, in part due to an audit by Public Health England.

In total, since the program’s launch on May 28, 14,085 people who tested positive for coronavirus had their case transferred to the contact tracing system, of whom 72.6% were reached.

In the first two weeks of operation, 87,639 people were identified as close contacts and reached through the contact tracing system out of 96,746 reported contacts.