Tom Jefferson|Chris B Del Mar|Liz Dooley|Eliana Ferroni|Lubna A. Al?Ansary|Ghada Bawazeer|Mieke van Driel|Mark Jones|Sarah Thorning|Elaine Beller|Justin Clark|Tammy Hoffmann|Paul Glasziou|John Conly
Physical interventions to interrupt or reduce the spread of respiratory viruses
University of Oxford|Bond University|Bond University|Regione del Veneto|King Saud University|King Saud University|University of Queensland|Ghent University|Bond University|Gold Coast Hospital|Bond University|Bond University|Bond University|Bond University|Alberta Health Services|Foothills Medical Centre|University of Calgary
background viral epidemics pandemics acute respiratory infections aris pose global threat examples influenza h1n1 caused h1n1pdm09 virus 2009 severe acute respiratory syndrome sars 2003 coronavirus disease 2019 covid19 caused sarscov2 2019 antiviral drugs vaccines may insufficient prevent spread update cochrane review published 2007 2009 2010 2011 evidence summarised review include results studies current covid19 pandemic objectives assess effectiveness physical interventions interrupt reduce spread acute respiratory viruses search methods searched central pubmed embase cinahl 1 april 2020 searched clinicaltrialsgov ictrp 16 march 2020 conducted backwards forwards citation analysis newly included studies selection criteria included randomised controlled trials rcts clusterrcts trials investigating physical interventions screening entry ports isolation quarantine physical distancing personal protection hand hygiene face masks gargling prevent respiratory virus transmission previous versions review also included observational studies however update sufficient rcts address study aims data collection analysis used standard methodological procedures expected cochrane used grade assess certainty evidence three pairs review authors independently extracted data using standard template applied previous versions review revised reflect focus rcts clusterrcts update contact trialists missing data due urgency completing review extracted data adverse events harms associated interventions main results included 44 new rcts clusterrcts update bringing total number randomised trials 67 included studies conducted covid19 pandemic six ongoing studies identified three evaluating masks conducted concurrent covid pandemic one completed many studies conducted nonepidemic influenza periods several studies conducted global h1n1 influenza pandemic 2009 others epidemic influenza seasons 2016 thus studies conducted context lower respiratory viral circulation transmission compared covid19 included studies conducted heterogeneous settings ranging suburban schools hospital wards highincome countries crowded inner city settings lowincome countries immigrant neighbourhood highincome country compliance interventions low many studies risk bias rcts clusterrcts mostly high unclear medicalsurgical masks compared masks included nine trials eight clusterrcts comparing medicalsurgical masks versus masks prevent spread viral respiratory illness two trials healthcare workers seven community low certainty evidence nine trials 3507 participants wearing mask may make little difference outcome influenzalike illness ili compared wearing mask risk ratio rr 099 95 confidence interval ci 082 118 moderate certainty evidence wearing mask probably makes little difference outcome laboratoryconfirmed influenza compared wearing mask rr 091 95 ci 066 126 6 trials 3005 participants harms rarely measured poorly reported two studies covid19 plan recruit total 72000 people one evaluates medicalsurgical masks n 6000 published annals internal medicine 18 nov 2020 one evaluates cloth masks n 66000 n95p2 respirators compared medicalsurgical masks pooled trials comparing n95p2 respirators medicalsurgical masks four healthcare settings one household setting uncertainty effects n95p2 respirators compared medicalsurgical masks outcomes clinical respiratory illness rr 070 95 ci 045 110 lowcertainty evidence 3 trials 7779 participants ili rr 082 95 ci 066 103 lowcertainty evidence 5 trials 8407 participants evidence limited imprecision heterogeneity subjective outcomes use n95p2 respirator compared medicalsurgical mask probably makes little difference objective precise outcome laboratoryconfirmed influenza infection rr 110 95 ci 090 134 moderatecertainty evidence 5 trials 8407 participants restricting pooling healthcare workers made difference overall findings harms poorly measured reported discomfort wearing medicalsurgical masks n95p2 respirators mentioned several studies one ongoing study recruiting 576 people compares n95p2 respirators medical surgical masks healthcare workers covid19 hand hygiene compared control settings included schools childcare centres homes offices comparison hand hygiene interventions control intervention 16 relative reduction number people aris hand hygiene group rr 084 95 ci 082 086 7 trials 44129 participants moderatecertainty evidence suggesting probable benefit considering strictly defined outcomes ili laboratoryconfirmed influenza estimates effect ili rr 098 95 ci 085 113 10 trials 32641 participants lowcertainty evidence laboratoryconfirmed influenza rr 091 95 ci 063 130 8 trials 8332 participants lowcertainty evidence suggest intervention made little difference pooled 16 trials 61372 participants composite outcome ari ili influenza study contributing comprehensive outcome reported pooled data showed hand hygiene may offer benefit 11 relative reduction respiratory illness rr 089 95 ci 084 095 lowcertainty evidence high heterogeneity trials measured reported harms two ongoing studies handwashing interventions 395 children outside covid19 identified one rct quarantinephysical distancing company employees japan asked stay home household members ili symptoms overall fewer people intervention group contracted influenza compared workers control group 275 versus 318 hazard ratio 080 95 ci 066 097 however stayed home infected family members 217 times likely infected found rcts eye protection gowns gloves screening entry ports authors conclusions high risk bias trials variation outcome measurement relatively low compliance interventions studies hamper drawing firm conclusions generalising findings current covid19 pandemic uncertainty effects face masks lowmoderate certainty evidence means confidence effect estimate limited true effect may different observed estimate effect pooled results randomised trials show clear reduction respiratory viral infection use medicalsurgical masks seasonal influenza clear differences use medicalsurgical masks compared n95p2 respirators healthcare workers used routine care reduce respiratory viral infection hand hygiene likely modestly reduce burden respiratory illness harms associated physical interventions underinvestigated need large welldesigned rcts addressing effectiveness many interventions multiple settings populations especially risk aris