Effectiveness of non-pharmaceutical interventions on SARS-CoV-2 transmission during the period January 2021 until May 2022: A systematic literature review
Authors: Vardavas Constantine I. , Nikitara Katerina , Aslanoglou Katerina , Marou Valia , Plyta Zinovia , Phalkey Revati , Leonardi Bee Jo , Condell Orla , Lamb Favelle , Suk Jonathan. E. 
Published: November 2023

ABSTRACTObjectivesIn response to the COVID-19 pandemic, countries implemented various non-pharmaceutical interventions(NPIs). With this systematic review, we investigated the effectiveness of NPIs in mitigating SARS-CoV-2 transmission by assessing empirical evidence and data obtained through modelling studies.DesignWe searched Medline(OVID) and EMBASE until 26 May 2022. The PICO framework was used to determine the eligibility of the studies. Populations were restricted to studies on humans, and there was no geographical limitation. The included articles assessed NPIs at the regional or national level as mitigation measures against SARS-CoV-2 transmission for human population without geographical limitation. Unmitigated SARS-CoV-2 transmission or the period before the implementation of the assessed NPI were used as the comparator.Main outcome measuresOutcome indicators were extracted and included COVID-19 cases, incidence and peaks, reproduction rate, growth rate, case mortality, and hospital and Intensive Care Unit admissions. Due to the heterogeneity between studies, statistical analysis was not possible and hence the results were presented narratively.Results49 studies were included; 21 based on empirical evidence and 28 modelling studies. Among the latter, the effectiveness of facemasks was evaluated in 11 studies, five assessed stay-at-home orders and five school closures. Regarding face mask use, the majority of studies presented a beneficial effect when appropriate social distancing measures could not be maintained. Restrictions on mass gatherings, stay-at-home-orders and lockdown measures were found to be effective in reducing SARS-CoV-2 transmission when timely and properly implemented. The results related to school closures were inconclusive.ConclusionsThis systematic review assesses the effectiveness of NPIs in reducing SARS-CoV-2 transmission from January 2021 until May 2022. It suggests the importance of timely implementation and the optimised impact when implementing multiple NPIs in parallel. Continuous monitoring of the effectiveness of NPIs is required to determine the most suitable nature, time, and duration of the implemented NPIs.What is already known on this topicPrior to this study, it was recognised that in response to the COVID-19 pandemic, various non-pharmaceutical interventions (NPIs) such as hygiene measures, face mask usage, travel restrictions, social distancing, and contact tracing were implemented worldwide. The scientific community has been assessing the effectiveness of these NPIs in mitigating the pandemic’s impact on public health and the economy.What this study addsThis systematic review contributes by presenting updated and comprehensive evidence regarding the effectiveness of NPIs as a means of mitigating SARS-CoV-2 transmission, using both real-world evidence and data obtained through modelling studies. The study affirms that the timely application of NPIs, including the use of face masks, stay-at-home orders, restrictions on mass gatherings, and school closures, substantially reduced COVID-19 cases and fatalities. It underscores the significance of employing multiple NPIs in tandem for heightened effectiveness within future respiratory pandemics. The review emphasises the necessity for ongoing assessment of NPI efficacy, taking into account factors such as public compliance, vaccination rates, and the prevalence of virus variants.How this study might affect research, practice, or policyThe findings of this study carry various implications. Firstly, they inform policymakers about the critical importance of promptly implementing NPIs and employing them in combination to manage respiratory pandemics. Secondly, the results underscore the enduring relevance of NPIs even as pandemic vaccination campaigns progress. Thirdly, the study highlights the need for standardized methodologies for evaluating the effectiveness of NPIs. Lastly, this review can guide future public health strategies by offering valuable insights into the impact of different interventions on pandemic control.