The effectiveness of non-pharmaceutical interventions in reducing SARS-CoV-2 transmission and COVID-19 incidence and mortality: systematic review and meta-analysis

Objective: The novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents a great challenge to public health and economy globally. Non-pharmaceutical interventions (NPIs) have been used as a first-line prevention against SARS-CoV-2 transmission. The objective of the study was to review the evidence on the effectiveness of NPIs in reducing COVID-19 incidence and mortality, and SARS-CoV-2 transmission.
Data sources: Electronic databases MEDLINE, EMBASE, CINAHL, Biosis, Joanna Briggs, Global Health and WHO COVID-19 database (preprints) were searched; and review of search results, data extraction, meta-analysis, and risk of bias assessment were performed.
Eligibility criteria for selecting studies: Observational and interventional studies assessing the effectiveness of NPIs in reducing COVID-19 incidence and mortality, and SARS-CoV-2 transmission were included.
Main outcome measures: The main outcome measure was incidence of COVID-19. Secondary outcomes included transmission of SARS-CoV-2 and mortality.
Data synthesis: DerSimonian Laird random-effects meta-analyses were performed to investigate the effect of face masks, hand hygiene and physical distance measures on COVID-19 incidence. Pooled effect estimates with their 95% confidence interval (CI) were computed and heterogeneity among studies was detected using Cochran’s Q test and the I2 metrics with all p values being two-tailed.
Results: Overall, 72 studies met the inclusion criteria, out of which 35 evaluated individual NPIs, and 37 assessed multiple NPIs as a “package of interventions” and were included as supplementary material. Eight out of 35 studies were included in the meta-analyses, which indicated an association with reduction in the incidence of COVID-19; handwashing (relative risks (RR)= 0.47, 95%CI: 0.19 to 1.12, I2=12%), face masks (RR= 0.47, 95%CI: 0.29 to 0.75, I2=84%) and physical distance (RR= 0.75, 95%CI: 0.59 to 0.95, I2=87%). Due to heterogeneity of studies, meta-analyses were not possible for outcomes measuring quarantine/isolation, universal lockdowns and border, school and workplace closures. The effects of these interventions were synthesised descriptively.
Conclusions: This systematic review and meta-analysis suggests that several NPIs, including use of handwashing, face masks, and physical distancing, were associated with reductions in COVID-19 incidence. Public health efforts to implement NPIs should consider community health and socio-cultural needs and future research is needed to better understand NPI effectiveness in the context of COVID-19 vaccination.