Filling the Knowledge Gap in Public Health and Social Measures

On March 15, 2023, the IANPHI Europe Network hosted a webinar to discuss the knowledge gap in public health and social measures (PHSMs), also known as non-pharmaceutical interventions (NPIs).

Throughout the world, PHSMs have been implemented to limit the spread of COVID-19. NPHIs play a key role in advising governments about the use of such measures – which, how and when to implement. Providing such advice has been challenging due to the limited scientific evidence on the effectiveness of these types of measures, including their unintended consequences. The evidence base consists largely of logical arguments and observational data, and there have been very few randomized trials of PHSMs conducted, both before and during the pandemic. 

Moderated by Dr. Atle Fretheim of the Norwegian Institute of Public Health, the session offered presentations of panelists from Germany's Robert Koch Institute, Public Health Wales and Denmark's Statens Serum Institut about the role of NPHIs in contributing to filling the knowledge gap.

Dr. Fretheim opened the session by highlighting the lack of consensus on the impact of NPIs on reducing transmission of COVID-19 and other infectious agents and difficulty in quantifying the negative consequences. He pointed to the contrast between the massive effort in vaccinology and clinical medicine during the pandemic and the rarity of randomized trials on PHSMs.

Presentation by Dr. Charbel El Bcheraoui, Robert Koch Institute, Germany

Dr. Charbel El Bcheraoui explained the importance of NPHIs in providing strategic information for policy-making during the COVID-19 pandemic. He talked about the need for a multi-layer model of evidence, including secondary data analysis and evidence review, to measure the effectiveness of PHSMs. He also reflected on the need for additional evidence, such as randomized trials, to inform decision-making.

Dr. El Bcheraoui discussed how countries implemented different strategies to combat the pandemic, and how different interventions affected the number of cases. He also presented the results of a systematic review of 34 papers that he conducted with colleagues and published in the Journal of Infection[1], which compared two NPIs to each other in terms of their effectiveness. He concluded that school closures, public event bans, and public information campaigns were effective interventions, while transport closures, testing strategies, and contact tracing were not as effective. He also referred to the complexity of interventions and the limited capacity of public health emergency workforce.

See Dr. El Bcheraoui's slides

Presentation by Prof. Fu-Meng Khaw, Public Health Wales, United Kingdom

Prof. Fu-Meng Khaw described the context of Wales as a devolved nation in the UK, and the Welsh government's response to the COVID-19 pandemic. He highlighted the importance of NPIs, such as self-isolation, shielding, and welfare benefits, to protect the population. He also discussed the need to ask questions about the effectiveness of complex interventions, and the need to make sense of evidence in a dynamic way.

The Welsh government set up a Technical Advisory Group to provide timely access to scientific and technical information and established a COVID-19 Evidence Center with a 3-million-pound investment, and commissioning research to inform policy and provision of services in health and social care. The Evidence Center focused on reviewing existing research evidence, while Public Health Wales conducted surveys and modeling to inform risk assessment and interventions.

Prof. Khaw concluded by reflecting on the hierarchy of evidence in the context of a pandemic and the disproportionate number of randomized controlled trials (RCTs) for non-pharmaceutical interventions compared to pharmaceutical interventions. “How might we design an RCT? And how might we prepare ourselves to implement an RCT?”, he asked.

See Prof. Khaw's slides

Presentation by Dr. Henrik Ullum, CEO of Denmark’s Statens Serum Institut

Dr. Henrik Ullum first outlined the role of the Statens Serum Institut (SSI) in providing research, sequencing, dashboards, reports, and advice to the Danish government during the pandemic. He continued by presenting a randomized control trial he conducted with fellow researchers before taking on the role of CEO of SSI, to study the effectiveness of wearing masks in Denmark during the COVID-19 pandemic. Despite the challenges they faced in staffing, equipment, and bureaucracy, they were able to successfully recruit 6,000 participants and randomly assign them into a mask-wearing or control group. The results showed no statistical difference between the two groups, with 1.8% of the control group and 2.1% of the intervention group becoming infected. After submitting the paper to various journals, the team faced difficulties due to the political implications of the results before finally being published[2]. Dr. Ullum concluded that medical decisions should be based on combined evidence, not on a single study, and that the lack of perfect evidence should not prevent action in a crisis, which was the case with the COVID-19 pandemic.

See Dr. Ullum's slides


Dr. Fretheim and Dr. Ullum discussed the possibility of conducting randomized trials to study the effectiveness of interventions during pandemics. They agreed that research should be conducted in peacetime, as well as having playbooks ready to roll out during a crisis. Dr. El Bcheraoui added that evidence-based public health should be considered, and that randomized trials are not the only way to evaluate interventions. He suggested that providing masks to participants could yield different results depending on the type of mask.

All three panelists then discussed the importance of considering a combination of methods to address the question of how to best prevent the spread of COVID-19. They suggested collecting data on the outputs of contact tracing, establishing a think tank to map out interventions, and increasing the sample size of studies to get more accurate results. They also discussed the importance of preparing for the next pandemic and having an ethical framework in place.

Dr. Ullum and Dr. El Bcheraoui talked about the difficulty of maintaining scientific independence in a politically charged environment, as well as the importance of using data to monitor societal activity during a pandemic.


[1]Mendez-Brito A, El Bcheraoui C, Pozo-Martin F. Systematic review of empirical studies comparing the effectiveness of non-pharmaceutical interventions against COVID-19. Journal of Infection. 2021;83(3):281-93.

[2]Bundgaard H, Bundgaard JS, Raaschou-Pedersen DET, von Buchwald C, Todsen T, Norsk JB, Pries-Heje MM, Vissing CR, Nielsen PB, Winsløw UC, Fogh K, Hasselbalch R, Kristensen JH, Ringgaard A, Porsborg Andersen M, Goecke NB, Trebbien R, Skovgaard K, Benfield T, Ullum H, Torp-Pedersen C, Iversen K. Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers: A Randomized Controlled Trial. Ann Intern Med. 2021 Mar;174(3):335-343. doi: 10.7326/M20-6817. Epub 2020 Nov 18. PMID: 33205991; PMCID: PMC7707213.

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