The first pilot of voluntary "mass testing" for people without Covid symptoms was associated with an overall 25% reduction in Covid-19-related hospital admissions, including an initial 43% reduction with assistance, according to a study published by The BMJ .
Assuming this effect was causal, the researchers say the pilot prevented 6,829 infections and led to 239 fewer hospital admissions in the city of Liverpool, before being rolled out to the rest of the UK.
If causal, this equates to more than 200 fewer hospital admissions than expected without this intervention, researchers say
The transmission of the Covid-19 virus by asymptomatic people has been a great challenge for controlling the pandemic. These latest findings show that large-scale voluntary community testing for Covid-19 can potentially reduce transmission of the virus and prevent hospitalizations.
The pilot, known as Covid-SMART, offered voluntary supervised lateral flow testing to all people over the age of 5 without symptoms living or working in Liverpool from November 6, 2020 to January 2, 2021. The aim was Identify infectious people sooner and interrupt transmission.
Covid-SMART coincided with the start of the UK’s second national lockdown (5 November – 2 December 2020). At the time, Liverpool’s unvaccinated population had the highest Covid-19 case rate in the country.
The researchers wanted to know if these large-scale tests were effective in reducing Covid-19-related hospital admissions.
To do this, they compared weekly Covid-19-related hospital admissions between the pilot (intervention) population with a control population selected from the rest of England with previous Covid-19 hospital admissions and similar sociodemographic factors to the intervention population.
When the analysis was restricted to the first month of the pilot (November 6 to December 3, 2020), the results show that it was associated with a 43% reduction in Covid-19-related hospital admissions in Liverpool compared to the control population. In absolute numbers this is equivalent to 146 fewer admissions in the period up to December 3, 2020.
However, the researchers emphasize that this was a time of intensive testing with military assistance when Liverpool was under higher lockdown restrictions (Tier 3) than many other areas of the country.
When the analysis was extended over the entire intervention period (November 6, 2020 to January 2, 2021) and regional differences in lockdown restrictions were taken into account, a 25% reduction in hospital admissions was observed related to covid-19 (equivalent to 239 fewer admissions) compared to the control population.
This is an observational study and the researchers emphasize that care should be taken when interpreting the findings in the context of different variants, immunity levels and testing policies. Furthermore, they cannot rule out the possibility that other unmeasured (confounding) factors may have influenced their results.
However, their approach ensured that control areas were likely to have been affected by similar coronavirus transmission patterns before the introduction of CovidSMART in Liverpool, and the results were similar after further analysis, suggesting they are robust.
As such, they say: "It is plausible that the main effect in our analysis is causally related to the Covid-SMART intervention, especially as the study period predates the main Covid-19 vaccination rollout."
They note that large-scale community testing is a complex intervention, where one person’s testing can affect the Covid risk behavior of another (e.g. a family member) and therefore the effect of the test. It is not a simple relationship between a test and a chain of virus transmission. They also emphasize that success depends on high levels of acceptance and effective support to enable the isolation of infectious people and their close contacts.
But they say their findings suggest that even where uptake is uneven and barriers to effective isolation exist, "widespread community testing can potentially reduce transmission and subsequent hospital admissions, at least in the short term."
