Testing for COVID-19 and tracing the prior contacts of those found to be infected are crucial measures for slowing the disease’s spread, but the test and trace method is inadequate unless combined with other measures, researchers said Wednesday.
By itself, the test-and-trace approach can reduce the virus’ reproduction rate, or R number, by 26 percent, they reported in The Lancet Infectious Diseases, using mathematical models to examine data from previously published studies.
Test and trace method can reduce COVID-19 reproduction rate
The reproduction rate measures the number of people in a population, on average, infected by each person carrying the virus.
Anything above “1” means the disease is continuing to expand; below that threshold, it will eventually peter out.
Some countries that brought the spread of COVID-19 under control but are now struggling to prevent a resurgence have R numbers well above 1.
In France, for example, it hovered at about 1.33 during the first week of August, according to national health authorities.
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But the new finding comes with a caveat, said lead author Nicholas Grassly, a professor at Imperial College’s School of Public Health.
“Our results show that test and trace can help reduce the R number but needs to be carried out effectively and quickly to do so,” he said in a statement.
Concretely, that means immediate testing with the onset of symptoms and results within 24 hours; the quarantine of contacts, also within 24 hours; and the identification of 80 percent of cases and contacts.
Very few countries — notably South Korea, Taiwan and Germany — have come close to staying within these guidelines, and most are still falling well short.
In France, for example, it generally take days to get an appointment for a so-called PCR nasal test, and on average 3.5 days for a result, according to official figures.
Relying on “herd immunity” not a viable option
In the United States and the UK, delays can be even longer.
Even if nations do adhere to these guidelines, it will still not be enough to bring the infection rate down sufficiently by itself, the new study concludes.
“Test and trace alone won’t be enough to control transmission in most communities, and other measures alongside will be needed to bring the R number below 1,” said Grassly.
Weekly screening of high-risk groups such as health and social-care workers — regardless of whether they have symptoms or not — can reduce transmission by an additional 23 percent, his team found.
Experts are still unsure as to what percentage of a population must be immune — a threshold known as “herd immunity” — to prevent the virus from continuing to spread.
Estimates range from below 50 to 70 percent.
It is possible that some of the hardest hit regions — New York City, northern Italy — may be close to these levels, but at a national scale the numbers are still far lower, probably barely in double digits.
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WHO emergencies director Michael Ryan said Tuesday that the planet was “nowhere close to the levels of immunity required to stop this disease”.
People should “not live in hope of herd immunity being our salvation. Right now, that is not a solution,” he added.
A vaccine, of course, would also provide immunity, but is unlikely to be available until next year.
Currently, only people who have fought off COVID-19 and survived have some degree of immunity, though it remains unclear how robust it is and how long it lasts.
It is also unclear the extent to which people with mild or asymptomatic cases have immunity at all.
The novel coronavirus has killed nearly 775,000 people and infected almost 22 million since the outbreak emerged in China last December, according to a tally from official sources compiled.
Pakistan’s COVID-19 testing efforts: can test and trace be used within Pak?
According to Our World in Data, the latest estimate of Pakistan’s daily tests per thousand people is 0.1 as of July 16, a rather sharp decline from 0.13 tests in June. Experts believe that current testing has dropped by at least a quarter.
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As per the National Command Operation Center (NCOC), Pakistan has a total testing capacity of 71,780 tests per day, with 133 testing laboratories in total. Currently, it is utilizing only about 40% of the capacity, according to the Ministry of National Health Services Regulation and Coordination.
According to official figures, it has performed 5,301 tests on August 1st in Punjab while the capacity was said to be 17,000 per day. Of the total tests, around 7,000 were being performed officially while others in the private sector.
Some health and medical experts believe that the tests were reduced when the positive cases ratio dropped to 10 per cent in Punjab. They were of the view that the Punjab government has cut down the number of tests to avoid wastage of funds because of the continuous decrease in positive ratio.
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Although, Pakistan has seen the brunt of the coronavirus pandemic within its borders pass, the threat of increasing infections still looms as testing is still below the potential capacity. The test and trace method can be useful in Pakistan in order to reduce the reproduction rate of the virus, however due to decreasing daily testing it can be argued whether the new measure will go in vain even if introduced. Thus, the efficacy of the test and trace measure remains to be unproven within Pakistan.
AFP with additional input by GVS News Desk