24 August 2023
Non-pharmaceutical interventions (NPIs), when applied in packages that combine a number of measures with complementary effects, were unequivocally effective in reducing the spread of infections during the COVID-19 pandemic, a major Royal Society report has found. NPIs are measures that are not drugs or vaccines aimed at reducing transmission of an infectious disease.
The report, COVID-19: examining the effectiveness of non-pharmaceutical interventions, reviewed the scientific evidence gathered during the pandemic for six groups of NPIs and their effectiveness in reducing transmission of the SARS-CoV-2 virus: masks and face coverings; social distancing and ‘lockdowns; test, trace and isolate; travel restrictions and controls across international borders; environmental controls; and communications.
It found, when assessed individually, there was positive – if limited – evidence of transmission reduction from many of the NPIs used in the pandemic.
However, the evidence of an effect was clear when countries used combinations of NPIs, and a small number of nations and regions were able to contain cases at very low numbers for up to the first 18 months of the pandemic.
Additionally, evidence showed NPIs were most effective when the intensity of transmission was low, supporting their use early in a pandemic and at first sign of resurgence.
NPIs are typically the only controls available in the early stages of responding to an emerging infectious disease, before the development of drug treatments, vaccines, and other therapies.
However, as was seen around the world during COVID-19, their use can have adverse personal, educational, and economic consequences – making robust assessment of their effectiveness essential.
Professor Sir Mark Walport, Foreign Secretary of the Royal Society and chair of the report’s expert working group, said: “COVID-19 was the first global pandemic in human history where the use of non-pharmaceutical interventions bought time for the development of effective treatments and vaccines that saved many lives.
“This report seeks to answer important questions about which NPIs helped limit infections, and in what circumstances?
“There is sufficient evidence to conclude that early, stringent implementation of packages of complementary NPIs was unequivocally effective in limiting SARS-CoV-2 infections.
“That does not mean every NPI was effective in every setting, or at all times, but learning the lessons from the wealth of research generated in this pandemic will be key to equipping ourselves for the next one.”
The report draws together the findings of six expert-led evidence reviews, published today (24 August) in a special themed issue of the peer-reviewed journal Philosophical Transactions of the Royal Society A.
These reviews examined thousands of published studies, and applied rigorous inclusion criteria to identify papers that were suitably robust for inclusion in each review category.
While a small number of randomised controlled trials (RCTs) were conducted during the pandemic, the majority of evidence available comes from observational studies.
Using observational data does influence the certainty of conclusions that can be drawn from the reviews, but the report concludes clear signals of effectiveness can be seen from the numerous, high-quality, rigorously conducted observational studies included.
Key findings from the report include:
For the future, the report recommends establishing international protocols for conducting RCTs and observational research on NPIs in advance of further pandemics. This would greatly improve the ability to evaluate the consequences of differences in implementation internationally and help to disaggregate their effects on different social groups and demographics.
Future research plans should also consider the costs as well as the benefits of NPIs, in terms of their impacts on livelihoods, economies, education, social cohesion, physical and mental wellbeing.