KUALA LUMPUR, Sept 6 — Local research projects that effective contact tracing, even with low vaccination rates, reduces daily Covid-19 cases up to nine times more than poor contact tracing coupled with high inoculation.
The preprint paper posted by Dr Dhesi Baha Raja et al last August 31, which has not yet been peer reviewed, used a deterministic SEIRV model with contact tracing and vaccination components to investigate the effect of contact tracing on Covid-19 transmission and infection in the context of rising vaccination rates.
Dr Dhesi’s paper estimated that daily untraced, symptomatic Covid-19 infections would peak at 3.35 million new cases in 41 days if only 30 per cent of contacts of each coronavirus case is successfully traced and 1.5 per cent of the population is vaccinated daily (480,000 doses administered a day).
On the other hand, a scenario of 90 per cent contact tracing effectiveness combined with a 1 per cent vaccination rate (320,000 doses administered daily) managed to delay the peak to Day 72 with just 381,000 cases, nearly 780 per cent lower than the previous combination of poor contact tracing and high inoculation.
The same trends were observed for asymptomatic infections.
A combination of 30 per cent contact tracing effectiveness and a 1.5 per cent vaccination rate led to a peak of 1.46 million new untraced, asymptomatic cases on Day 42, about 702 per cent higher than a peak of 182,000 cases on Day 74 in a scenario of 90 per cent contact tracing effectiveness and a 1 per cent vaccination rate.
“In this simulation study, we found effective contact tracing to be a critical component in Covid-19 control,” lead researcher Dr Dhesi told CodeBlue.
“Interventions to improve the effectiveness and efficiency of contact tracing strategy, such as technology and automation, should be considered.
“While vaccination rates have progressively increased in Malaysia and some parts of the world, efficient contact tracing must be rapidly implemented to reach, find, test, isolate, and support the affected populations to bring the pandemic under control,” added the chief medical innovation officer of Ainqa Health Malaysia, a health tech outfit, that funded the study.
Nearly half of Malaysia’s total population has been fully vaccinated against Covid-19 to date. Dr Dhesi’s paper estimated that Malaysian authorities currently only manage to trace 30 per cent to 40 per cent of contacts of every Covid-19 case.
Two other scenarios were simulated with contact tracing effectiveness fixed at 90 per cent and 35 per cent respectively, while vaccination rates varied at between 0.8 per cent (260,000 doses administered daily) and 1.4 per cent (450,000 doses administered daily) in both scenarios.
At 35 per cent contact tracing effectiveness, daily untraced symptomatic Covid-19 cases could peak at 1.2 million on Day 54 even with a high 1.4 per cent vaccination rate. A similar outcome was observed for daily untraced asymptomatic infections in the same scenario, peaking at an estimated 540,000 on Day 57.
In the scenario of 90 per cent contact tracing effectiveness, daily untraced symptomatic cases could still be reduced to about 381,000 cases at the peak on Day 70 even with a low 1 per cent vaccination rate.
At 90 per cent contact tracing effectiveness with vaccination rates ranging between 0.8 per cent and 1.4 per cent per day, the peaks for all permutations ranged between 107,000 and 207,000 daily untraced asymptomatic cases, occurring at around the same time between Day 68 and Day 73.
In this scenario of fixed contact tracing effectiveness, the difference in the peak number of new untraced asymptomatic cases was only about 100,000 between high and low vaccination rates.
“The increase in vaccination rate could only delay the peak but failed to lower the peak significantly,” researchers wrote.
When the daily vaccination rate was fixed at 1.4 per cent (450,000 doses given daily), new untraced symptomatic Covid-19 cases peaked at about 3.5 million on Day 40 with a low 30 per cent contact tracing effectiveness.
When contact tracing effectiveness rose to 70 per cent, the peak was delayed by about 15 days with approximately one million cases, about 29 per cent of cases estimated when contact tracing was at 30 per cent effectiveness.
The number of daily untraced asymptomatic coronavirus infections peaked at about 1.52 million on Day 42 at 30 per cent contact tracing effectiveness combined with a 1.4 per cent vaccination rate.
When contact tracing effectiveness increased to 70 per cent, the peak was delayed by about 17 days, hitting 459,000 daily untraced asymptomatic cases. This marked a 70 per cent reduction from estimated cases when contact tracing effectiveness was 30 per cent.
“It can be observed that a contact tracing effectiveness of 90 per cent would almost flatten the curve,” said researchers.
Across the board, at a 1.4 per cent vaccination rate, 70 per cent contract tracing effectiveness will reduce peak incidence for both asymptomatic and symptomatic Covid-19 cases by 70 per cent compared to 30 per cent contact tracing effectiveness. More effective contact tracing delayed and lowered the peaks for both symptomatic and asymptomatic infections.