Systematic review objective

The 2011 review Aerosol-generating procedures and risk of transmission of acute respiratory diseases: A systematic review (149) assessed the clinical evidence on the risk of transmission of ARIs to health-care workers exposed to aerosol-generating clinical procedures compared with the risk to workers not exposed to the same procedures.

Methods

The authors used a predefined strategy to search electronic health-care databases including PubMed, MEDLINE, EMBASE, CINAHL, The Cochrane Library (Issue 10, 2010), University of York Centre for Reviews and Dissemination databases, EuroScan, LILACS, Indian Medlars, Index Medicus for South East Asia and international health technology agencies; they also conducted a focused Internet search. Information sources were limited to health technology assessments, systematic reviews, meta-analyses, randomized controlled trials (RCTs), non-randomized controlled studies and guidelines published between 1 January 1990 and 22 October 2010. The search strategy contained no language limitation. Studies included in the review were those that examined the relevant study population (health-care workers caring for patients with ARIs), intervention (provision of care for patients undergoing aerosol-generating procedures), comparator (provision of care for patients not undergoing aerosol-generating procedures) and outcome (transmission of ARI from patient to health-care worker).

Of the 1862 abstracts identified by electronic search and screened against inclusion criteria, 86 citations were retrieved. Of these, 10 relevant non-randomized studies (5 case–control and 5 retrospective cohort studies) met the criteria for inclusion in the systematic review (Fig. L.1). The quality of evidence was rated using the GRADE framework (47).

Figure L.1

Selection of publications for Aerosol-generating procedures and risk of transmission of acute respiratory diseases: A systematic review.

Results and conclusions

All studies included in the review assessed the transmission of SARS-CoV to health-care workers associated with the performance of potentially aerosol-generating procedures while caring for ill patients in hospital or intensive care unit settings during the SARS outbreaks of 2002–2003.

The most consistent statistically significant association of an increased risk of SARS transmission to workers was found in tracheal intubation (eight studies) (Table L.1 and Fig. L.2). Increased risk of SARS transmission was also reported in non-invasive ventilation (two studies), tracheotomy (one study), and manual ventilation before intubation (one study); however, these findings were identified from a limited number of very low quality studies, which makes interpretation difficult. There was no significant difference in the risk of SARS transmission between exposed and unexposed health-care workers for all other procedures evaluated – suction before intubation, suction after intubation, manual ventilation after intubation, bronchoscopy, nebulizer treatment, manipulation of oxygen mask, manipulation of bilevel positive airway pressure (BiPAP) mask, defibrillation, chest compressions, insertion of nasogastric tube, collection of sputum sample, high-frequency oscillatory ventilation, high-flow oxygen, endotracheal aspiration, suction of body fluid, administration of oxygen, chest physiotherapy and mechanical ventilation (Table L.1). All studies were rated very low quality according to GRADE criteria (47).

Table L.1

Summary of results from studies selected in the systematic review Aerosol-generating procedures and risk of transmission of acute respiratory diseases: A systematic review.

Figure L.2

CI, confidence interval; n, number of events; N, sample size; OR, odds ratio; SARS, severe acute respiratory syndrome

The findings suggest that some procedures potentially capable of generating aerosols are associated with increased risk of SARS transmission to health-care workers, with the most consistent association being across multiple studies identified with tracheal intubation. Other associations included non-invasive ventilation from two studies, and manual ventilation before intubation and tracheotomy, each from single studies. The authors note that these results must be interpreted in the context of the very low quality of the studies. A significant research gap was identified in this area: studies of higher methodological quality are required to provide more precise information about the risk of aerosol generation and the risk of transmission of microbes causing specific acute respiratory diseases, including influenza, from patients undergoing aerosol-generating procedures to health-care workers.

Systematic review objective

This 2011 review – Physical interventions to interrupt or reduce the spread of respiratory viruses (51) – examined evidence for the effectiveness of physical barriers (e.g. screening at entry ports, isolation, quarantine, social distancing, barriers, personal protection and hand hygiene) in reducing the spread of respiratory viruses. It represents an update of a previously conducted systematic review of the same topic in 2010 (266), with some adaptations designed to inform the review of the WHO interim guidelines Infection prevention and control of epidemic- and pandemic-prone acute respiratory diseases in health care, 2007 (16).

Methods

The authors used predefined criteria to search the relevant databases, including 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). Of 3775 titles identified, 3560 were scanned and excluded, 215 were retrieved in full text and 67 were selected for inclusion. Included studies were those that investigated any intervention intended to prevent transmission of respiratory viruses compared with no intervention or with another intervention and that measured several negative outcomes associated with respiratory virus transmission (i.e. death, number of cases of viral illness, severity of viral illness and proxies for the preceding outcomes).

Results and conclusions

After screening potential publications for inclusion criteria, a total of 67 studies were included in the review, comprising RCTs, cluster-RCTs and observational studies, with a mixed risk of bias. The review identified seven studies – four RCTs and three observational studies – that were not in the previous review (266).

The risk of bias for most of the RCTs and cluster-RCTs was high, with the exception of one cluster-RCT that was considered of medium risk of bias and one RCT that was considered of low risk of bias. Data from observational studies were of mixed quality. The results of the case–control studies were considered sufficiently homogeneous to allow pooling and meta-analysis. Most of the information sources studied SARS; therefore, applying the review findings to other diseases will require additional research.

The results of the best quality cluster-RCTs suggest that respiratory virus spread can be prevented by hygiene measures, such as handwashing, especially when interventions are aimed at young children or households with young children. The conclusion that hygiene measures reduce transmission from children to other members of the household was broadly supported by other studies, although these conclusions came from studies that have a greater potential for confounding. No conclusion could be drawn regarding the benefit of adding virucidals or antiseptics to standard handwashing. The pooled case-control studies suggested that implementing transmission barriers, isolation and hygiene measures are effective at reducing respiratory virus transmission. Facial masks (surgical masks or N95 respirators) were the intervention that was found to perform most consistently, and the evidence did not indicate superiority of N95 respirators over simple surgical masks in decreasing transmission of acute respiratory disease. One study found that screening at entry ports was associated with a marginal delay in spread; however, this association was not significant. The review found limited evidence that social distancing or spatial separation (i.e. keeping a distance of at least 1 m between infected patients and others) was effective. The results are summarized in Table L.2, below.

Table L.2

Summary of main results from the systematic review Physical interventions to interrupt or reduce the spread of respiratory viruses.

Systematic review objective

This 2011 review – Physical interventions to interrupt or reduce the transmission of respiratory viruses – resource use implications: A systematic review (207) – examined the economic literature related to resource implications and costs and cost effectiveness of physical barriers used to interrupt or reduce the spread of respiratory viruses. It was intended to supplement information provided in the Cochrane Review, Physical interventions to interrupt or reduce the spread of respiratory viruses (51) (Section L.2), and represents an important source of information for decision-makers considering the resource use implications of these interventions.

Methods

The authors used a peer-reviewed search strategy to search the following electronic bibliographic databases: EMBASE 1980 to 2010 Week 43, Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations and Ovid MEDLINE(R) 1950 to 2010, The Cochrane Library (2010, Issue 10), including the NHS Economic Evaluation Database (NHS EED), Health Economic Evaluations Database (HEED), CINAHL and PubMed. The initial search was completed in November 2010, with regular alerts established on EMBASE, MEDLINE and PubMed through April 2011. The publications identified were limited to economic studies published between 1995 and 2010. The search was not limited by language. Additional relevant information sources were sought through searches of the web sites of health technology assessment and related agencies, professional associations and other specialised databases, and of Google, Google Scholar and other Internet search engines, plus review of bibliographies and abstracts of key papers and consultation with experts.

The literature search yielded 1146 citations, the abstracts of which were screened for inclusion criteria. A total of 158 were retrieved for more detailed evaluation, of which 39 studies were subjected to full review. Seven studies reported information on resource use of physical interventions or assessed the cost effectiveness of physical interventions and were, therefore, selected for inclusion in the systematic review (Fig. L.3).

Figure L.3

Selection of publications for Physical interventions to interrupt or reduce the transmission of respiratory viruses – resource use implications: A systematic review. Steps for the selection of relevant studies on resource use

Results and conclusions

Using the GRADE appraisal methodology, the evidence provided by all seven studies was of very low quality, largely due to issues of study design, indirectness, and precision or sample size. The authors noted that, in some cases, the reliability of modelling results was questionable due to sensitivity to input assumptions. In addition, all economic studies included in the review were designed to address specific study questions and were conducted in settings subject to local recommendations and policies that differed from place to place. As a result, direct comparison of the findings and formulation of general conclusions was difficult.

A major finding of this review was the serious lack of high-quality research examining resource use and economic implications associated with PPE and other physical barriers for the interruption or reduction of respiratory virus transmission. In general, the current evidence suggests that the use of PPE (e.g. medical masks, respirators, eye protection, gloves and gowns) to reduce the burden of respiratory viruses may be economically attractive, particularly in situations of rapid or prolific transmission and high fatality rate. The authors noted that these results depend on multiple assumptions, including transmission rate, facility infection rate and compliance with the interventions. In addition, the results suggested that there is an increase in the use of physical interventions to interrupt or reduce the spread of respiratory viruses during epidemics and pandemics, with two studies indicating that PPE may actually be overused during pandemics. The authors concluded that, while appropriate use of PPE is likely to be cost effective in certain situations, overuse could eliminate the overall cost effectiveness.

The authors noted that generalizability of the results to different respiratory virus types and settings other than hospitals still needs to be evaluated.

Systematic review objective

This review – The effectiveness of vaccination of healthcare workers for the protection of patients at higher risk of acute respiratory disease: A systematic review (130) – examined evidence for the effectiveness of influenza and pneumococcal vaccination of health-care workers in protecting patients at higher risk of severe or complicated disease from ARI.

Methods

The authors used a predefined strategy to search electronic health-care databases including EMBASE, CINAHL, MEDLINE, PubMed, The Cochrane Library, J-Stage, BDSP, EASTVIEW, Index-F, eLIBRARY, WHO regional indexes, and the WHO portal of clinical trials; they also accessed relevant evidence-based reviews, guidelines and grey literature. Publications were reviewed against eligibility criteria in a three-stage process to ensure appropriate study types (experimental or observational study or systematic review), subject population (patients of all ages who were at higher risk of severe or complicated illness as a result of ARI), intervention (vaccination of any person providing health care to high-risk patients with influenza or pneumococcal vaccines in any dose, preparation or schedule), comparator (no vaccination, placebo or use of long-term prophylaxis) and outcome (cases of or consultations for ARI; cases of, consultations for or laboratory evidence of ILI where relevant; mortality from respiratory infection, ILI, acute respiratory disease or associated complications; or measurements of health-care usage due to respiratory infection, ILI or acute respiratory disease). Reference and citation tracking was undertaken for all citations meeting eligibility criteria at the full-text stage.

Of the 12 352 total citations identified, 11 234 were excluded following a review of the titles, 941 following a review of the abstracts, and 160 following review of the full text (Fig. L.4). A total of 20 papers were included, 17 from the original search and an additional 3 records identified from citation or reference tracking. Of these, 14 were primary research papers and 6 were reports of two systematic reviews.

Figure L.4

Selection of publications for The effectiveness of vaccination of healthcare workers for the protection of patients at higher risk of acute respiratory disease: A systematic review.

Results and conclusions

There was marked heterogeneity in the populations, interventions or exposures and outcomes considered, limiting the comparability of the included papers. Of the 14 primary research papers, 11 were in long-term residential care settings, and all were judged to be at risk of bias. Four were RCTs, and data from these had been pooled in a previous systematic review. This demonstrated a statistically significant protective effect with regard to measures of ILI and all-cause mortality among elderly residents. Additional observational data identified in this review suggested a uniform direction of effect across several measures of ILI, with a similar pattern for laboratory-confirmed influenza. The authors concluded that, although limited, a true underlying protective effect for patients at higher risk of severe or complicated ARI disease due to vaccination of health-care workers in long-term residential settings is likely (Table L.3).

Table L.3

Summary of findings from The effectiveness of vaccination of healthcare workers for the protection of patients at higher risk of acute respiratory disease: A systematic review.

The authors identified a major research gap in the topic area, noting that existing evidence provides little information about groups other than those in long-term residential settings. More research is required to determine the effectiveness of vaccination of health-care workers in protecting other higher-risk patient populations.