Fewer than six out of ten close contacts were reached according to the latest weekly figures, which also showed record numbers of in-person tests are not being returned within the promised 24-hour window.
Government scientific advisors have previously said that the system needs to be reaching eight out of ten close contacts of those testing positive for the CCP virus.
The system only approached that level in the summer, with success rates dropping over recent months as case numbers rise.
The latest figures, for the week ending October 8, show that just 59.6 percent of people were reached, down from 72 percent the week before.
The Government’s chief scientific adviser Sir Patrick Vallance accepted that there was “room for improvement” in the system.
However, he noted that the approach isn’t suited to higher levels of infection.
“Test, trace, and isolation becomes much more difficult to have an impact once numbers are high,” said Vallance. “It’s much more effective when numbers are low.”
“It’s really important to concentrate on numbers of contacts, isolation as quickly as you can, and getting things back as quickly as you can,” he said during a Downing Street briefing on Oct. 22. “Ideally, you get the whole process done within 48 hours.”
The system, which Prime Minister Boris Johnson had previously said would be “world-beating” has come under increasing pressure from a recent wave of positive tests.
The latest figures show that the system identified a total of over 250,000 close contacts—an increase of 15 percent in a week and part of what Public Health England (PHE) describes as a “sharp upward trend since the end of August.”
“For those where communication details were available, 75.1 [percent] were reached and asked to self-isolate,” said the PHE release.
The growing demand on the system is also impacting the turnaround of in-person test sites. Just 15 percent were able to deliver results within the 24-hour goal—less than half of the 32 percent achieved in the previous week.
In June, 94 percent of these tests were received within the 24-hour window.
A total of 101,494 people tested positive for the CCP virus according to the Test and Trace data, a 12 percent increase from the previous week, and the highest yet.
The figures come as a new study suggests the government’s decision not to test passengers flying into the UK was based on flawed analysis.
Instead of catching just 7 percent of infected travelers, as the government was advised earlier in the pandemic, testing on arrival could identify over 63 percent.
“Unlike 30-plus countries, including Germany and Italy, the UK has not introduced any form of scheme to test travelers for COVID-19,” said a statement from Oxera and Edge Health. The UK instead adopted a policy of 14-day quarantines along with “travel corridors.”
That policy was driven in part by PHE modelling that said only 7 percent of virus cases could be picked up through testing.
‘The way in which the PHE model is set up means that only a tiny proportion of infected passengers—those who become symptomatic or are asymptomatic but detectable by a PCR test during the flight—can be detected at arrival,” said George Batchelor, co-founder and director of Edge Health, an analytics firm that works with the NHS.
“This means the widely quoted 7 percent excludes anyone who is in theory detectable or symptomatic before the flight takes off.”
By contrast, Edge Health and Oxera estimate that up to 63 percent of infected passengers could be identified and prevented from entering the country with a testing scheme.