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KSR Number: KSRL1594

Physical interventions to interrupt or reduce the spread of respiratory viruses

  • Cochrane Database Syst Rev 2011, 7, CD006207, 10.1002/14651858.CD006207.pub4
  • Full report

Risk of Bias Assessment

Overall summary: Low risk of bias in the review

Bottom Line

The available evidence indicates that frequent hand washing, with or without adjunct antiseptics, barrier measures such as gloves and masks, with or without filtration apparatus, are likely to be useful for reducing transmission of epidemic respiratory viruses. There was insufficient data to adequately assess the effectiveness of global and high resource-intensive interventions such as screening at entry ports and social distancing.

Risk of Bias Assessment

Overall summary Low risk of bias in the review

Low

All domains were considered at low concern suggesting no substantial limitations with the review process.

A. Did the interpretation of findings address all of the concerns identified in Domains 1 to 4? Probably yes
B. Was the relevance of identified studies to the review's research question appropriately considered? Probably yes
C. Did the reviewers avoid emphasizing results on the basis of their statistical significance? Probably yes
Risk of bias in the review Low

Details of Review

Number of studies 67
Number of participants Unclear
Last search date October 2012
Review type Intervention
Objective To assess the effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses.
Population People of all ages
Interventions Any intervention to prevent viral animal to human or human to human transmission of respiratory viruses (screening at entry ports, isolation, quarantine, social distancing, barriers, personal protection and hand hygiene)

Antivirals and vaccines were excluded.
Comparator Another intervention, no intervention
Outcome Deaths, numbers of cases of viral illness, severity of viral illness, any proxies
Study design Individual level, cluster randomised, quasi randomised, cohort and case control designs

Results

The results of RCTs and cluster RCTs were not pooled, because of differences in definitions and comparisons between studies. The results of included RCTs were inconsistent, however, the highest quality cluster-RCTs suggested that respiratory virus spread can be reduced by hygienic measures, such as hand washing, especially in young children (under the age of 24 months).

There was insufficient data to adequately assess the effectiveness of global and high resource-intensive interventions such as screening at entry ports and social distancing.

All meta-analyses were of case-control studies. Meta-analysis of seven studies (n=2825) indicated that frequent hand washing (minimum of 11 times daily) resulted in lower infection rates (odds ratio [OR] 0.54, 95% confidence interval [CI] 0.44 to 0.67). A summary effect estimate, from seven studies (n=3216), indicated that simple mask wearing was was also effective in lowering infection rates (OR 0.32, 95%CI 0.26 to 0.39). meta-analysis of three studies (n=817) indicated that N95 respirator wearing was effective in lowering infection rates (OR 0.17, 95% CI 0.07 to 0.43). A pooled effect estimate from six studies (n=1836) indicated that wearing gloves was also effective in lowering infection rates (OR 0.32, 95% CI 0.23 to 0.45).

Full Risk of Bias Assessment

A published protocol was available for this review and no deviations from the protocol were reported. The objective of the review was clearly stated and appropriate inclusion criteria were defined. No restrictions, based on study characteristics or language, were reported.

1.1 Did the review adhere to pre-defined objectives and eligibility criteria? Probably yes
1.2 Were the eligibility criteria appropriate for the review question? Yes
1.3 Were eligibility criteria unambiguous? Yes
1.4 Were all restrictions in eligibility criteria based on study characteristics appropriate (e.g. date, sample size, study quality, outcomes measured)? Yes
1.5 Were any restrictions in eligibility criteria based on sources of information appropriate (e.g. publication status or format, language, availability of data)? Yes
Concerns regarding specification of study eligibility criteria Low

The Cochrane Central Register of Controlled Trials, MEDLINE, LILACS, Indian MEDLARS, IMSEAR and EMBASE were searched for relevant studies. The references of all included studies and the archives of the former MRC Common Cold Unit were screened to identify other potentially relevant studies. The full search strategy was provided and appeared adequate. No restrictions based on date, publication format, or language was reported. Two reviewers independently applied the inclusion criteria to all identified and retrieved articles.

2.1 Did the search include an appropriate range of databases/electronic sources for published and unpublished reports? Yes
2.2 Were methods additional to database searching used to identify relevant reports? Yes
2.3 Were the terms and structure of the search strategy likely to retrieve as many eligible studies as possible? Yes
2.4 Were restrictions based on date, publication format, or language appropriate? Yes
2.5 Were efforts made to minimise error in selection of studies? Yes
Concerns regarding methods used to identify and/or select studies Low

Two reviewers independently performed data extraction. Sufficient study characteristics appear to have been extracted to allow interpretation of results. The risk of bias of included RCTs was assessed using the Cochrane risk of bias tool and case control and cohort studies were assessed using the Newcastle-Ottawa scale.

3.1 Were efforts made to minimise error in data collection? Yes
3.2 Were sufficient study characteristics considered for both review authors and readers to be able to interpret the results? Yes
3.3 Were all relevant study results collected for use in the synthesis? Yes
3.4 Was risk of bias (or methodological quality) formally assessed using appropriate criteria? Yes
3.5 Were efforts made to minimise error in risk of bias assessment? Probably yes
Concerns regarding methods used to collect data and appraise studies Low

The synthesis included all relevant studies and was appropriate. The analysis methods were explained in the methodology section. The included studies had low to moderate heterogeneity. Sensitivity analysis was performed to assess the robustness of findings. Risk of bias was addressed in the synthesis.

4.1 Did the synthesis include all studies that it should? Yes
4.2 Were all pre-defined analyses reported or departures explained? Yes
4.3 Was the synthesis appropriate given the degree of similarity in the research questions, study designs and outcomes across included studies? Probably yes
4.4 Was between-study variation minimal or addressed in the synthesis? Yes
4.5 Were the findings robust, e.g. as demonstrated through funnel plot or sensitivity analyses? Yes
4.6 Were biases in primary studies minimal or addressed in the synthesis? Yes
Concerns regarding synthesis and findings Low

Abstract

Background Viral epidemics or pandemics of acute respiratory infections like influenza or severe acute respiratory syndrome pose a global threat. Antiviral drugs and vaccinations may be insufficient to prevent their spread. Objectives To review the effectiveness of physical interventions to interrupt or reduce the spread of respiratory viruses. Search methods We searched The Cochrane Library, the Cochrane Central Register of Controlled Trials (CENTRAL 2010, Issue 3), which includes the Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to October 2010), OLDMEDLINE (1950 to 1965), EMBASE (1990 to October 2010), CINAHL (1982 to October 2010), LILACS (2008 to October 2010), Indian MEDLARS (2008 to October 2010) and IMSEAR (2008 to October 2010). Selection criteria In this update, two review authors independently applied the inclusion criteria to all identified and retrieved articles and extracted data. We scanned 3775 titles, excluded 3560 and retrieved full papers of 215 studies, to include 66 papers of 67 studies. We included physical interventions (screening at entry ports, isolation, quarantine, social distancing, barriers, personal protection, hand hygiene) to prevent respiratory virus transmission. We included randomised controlled trials (RCTs), cohorts, case‐controls, before‐after and time series studies. Data collection and analysis We used a standardised form to assess trial eligibility. We assessed RCTs by randomisation method, allocation generation, concealment, blinding and follow up. We assessed non‐RCTs for potential confounders and classified them as low, medium and high risk of bias. Main results We included 67 studies including randomised controlled trials and observational studies with a mixed risk of bias. A total number of participants is not included as the total would be made up of a heterogenous set of observations (participant people, observations on participants and countries (object of some studies)). The risk of bias for five RCTs and most cluster‐RCTs was high. Observational studies were of mixed quality. Only case‐control data were sufficiently homogeneous to allow meta‐analysis. The highest quality cluster‐RCTs suggest respiratory virus spread can be prevented by hygienic measures, such as handwashing, especially around younger children. Benefit from reduced transmission from children to household members is broadly supported also in other study designs where the potential for confounding is greater. Nine case‐control studies suggested implementing transmission barriers, isolation and hygienic measures are effective at containing respiratory virus epidemics. Surgical masks or N95 respirators were the most consistent and comprehensive supportive measures. N95 respirators were non‐inferior to simple surgical masks but more expensive, uncomfortable and irritating to skin. Adding virucidals or antiseptics to normal handwashing to decrease respiratory disease transmission remains uncertain. Global measures, such as screening at entry ports, led to a non‐significant marginal delay in spread. There was limited evidence that social distancing was effective, especially if related to the risk of exposure. Authors' conclusions Simple and low‐cost interventions would be useful for reducing transmission of epidemic respiratory viruses. Routine long‐term implementation of some measures assessed might be difficult without the threat of an epidemic.