***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Please cite this paper as : MacIntyre et al. ( 2011 ) A cluster r and omized clinical trial comparing fit‐tested and non‐fit‐tested  N95 respirators to medical masks to prevent respiratory virus infection in health care workers . Influenza and Other Respiratory Viruses DOI : 10.1111/j.1750‐2659.2010.00198.x . Background We compared the efficacy of medical masks , N95 respirators ( fit tested and non fit tested ) , in health care workers ( HCWs ) . Methods A cluster r and omized clinical trial ( RCT ) of 1441 HCWs in 15 Beijing hospitals was performed during the 2008/2009 winter . Participants wore masks or respirators  during the entire work shift for 4 weeks . Outcomes included clinical respiratory illness ( CRI ) , influenza‐like illness ( ILI ) , laboratory‐confirmed respiratory virus infection and influenza . A convenience no‐mask/respirator group of 481 health workers from nine hospitals was compared . Findings The rates of CRI ( 3·9 % versus 6·7 % ) , ILI ( 0·3 % versus 0·6 % ) , laboratory‐confirmed respiratory virus ( 1·4 % versus 2·6 % ) and influenza ( 0·3 % versus 1 % ) infection were consistently lower for the N95 group compared to medical masks . By intention‐to‐treat analysis , when P values were adjusted for clustering , non‐fit‐tested N95 respirators were significantly more protective than medical masks against CRI , but no other outcomes were significant . The rates of all outcomes were higher in the convenience no‐mask group compared to the intervention arms . There was no significant difference in outcomes between the N95 arms with and without fit testing . Rates of fit test failure were low . In a post hoc analysis adjusted for potential confounders , N95 masks and hospital level were significant , but medical masks , vaccination , h and washing and high‐risk procedures were not . Interpretation Rates of infection in the medical mask group were double that in the N95 group . A benefit of respirators is suggested but would need to be confirmed by a larger trial , as this study may have been underpowered . The finding on fit testing is specific to the type of respirator used in the study and can not be generalized to other respirators . Trial registration Australian New Zeal and Clinical Trials Registry ( ANZCTR ) , ACTRN : ACTRN12609000257268 ( http://www.anzctr.org.au ) BACKGROUND During the influenza A(H1N1 ) p and emic , antiviral prescribing was limited , vaccines were not available early , and the effectiveness of nonpharmaceutical interventions ( NPIs ) was uncertain . Our study examined whether use of face masks and h and hygiene reduced the incidence of influenza-like illness ( ILI ) . METHODS A r and omized intervention trial involving 1437 young adults living in university residence halls during the 2006 - 2007 influenza season was design ed . Residence halls were r and omly assigned to 1 of 3 groups-face mask use , face masks with h and hygiene , or control- for 6 weeks . Generalized models estimated rate ratios for clinical ly diagnosed or survey-reported ILI weekly and cumulatively . RESULTS We observed significant reductions in ILI during weeks 4 - 6 in the mask and h and hygiene group , compared with the control group , ranging from 35 % ( confidence interval [ CI ] , 9%-53 % ) to 51 % ( CI , 13%-73 % ) , after adjusting for vaccination and other covariates . Face mask use alone showed a similar reduction in ILI compared with the control group , but adjusted estimates were not statistically significant . Neither face mask use and h and hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI cumulatively . CONCLUSIONS These findings suggest that face masks and h and hygiene may reduce respiratory illnesses in shared living setting s and mitigate the impact of the influenza A(H1N1 ) p and emic . TRIAL REGISTRATION Clinical Trials.gov identifier : NCT00490633 BACKGROUND Health care workers outside surgical suites in Asia use surgical-type face masks commonly . Prevention of upper respiratory infection is one reason given , although evidence of effectiveness is lacking . METHODS Health care workers in a tertiary care hospital in Japan were r and omized into 2 groups : 1 that wore face masks and 1 that did not . They provided information about demographics , health habits , and quality of life . Participants recorded symptoms daily for 77 consecutive days , starting in January 2008 . Presence of a cold was determined based on a previously vali date d measure of self-reported symptoms . The number of colds between groups was compared , as were risk factors for experiencing cold symptoms . RESULTS Thirty-two health care workers completed the study , result ing in 2464 subject days . There were 2 colds during this time period , 1 in each group . Of the 8 symptoms recorded daily , subjects in the mask group were significantly more likely to experience headache during the study period ( P < .05 ) . Subjects living with children were more likely to have high cold severity scores over the course of the study . CONCLUSION Face mask use in health care workers has not been demonstrated to provide benefit in terms of cold symptoms or getting colds . A larger study is needed to definitively establish noninferiority of no mask use Background There are sparse data on whether non-pharmaceutical interventions can reduce the spread of influenza . We implemented a study of the feasibility and efficacy of face masks and h and hygiene to reduce influenza transmission among Hong Kong household members . Methodology /Principal Findings We conducted a cluster r and omized controlled trial of households ( composed of at least 3 members ) where an index subject presented with influenza-like-illness of < 48 hours duration . After influenza was confirmed in an index case by the QuickVue Influenza A+B rapid test , the household of the index subject was r and omized to 1 ) control or 2 ) surgical face masks or 3 ) h and hygiene . Households were visited within 36 hours , and 3 , 6 and 9 days later . Nose and throat swabs were collected from index subjects and all household contacts at each home visit and tested by viral culture . The primary outcome measure was laboratory culture confirmed influenza in a household contact ; the secondary outcome was clinical ly diagnosed influenza ( by self-reported symptoms ) . We r and omized 198 households and completed follow up home visits in 128 ; the index cases in 122 of those households had laboratory-confirmed influenza . There were 21 household contacts with laboratory confirmed influenza corresponding to a secondary attack ratio of 6 % . Clinical secondary attack ratios varied from 5 % to 18 % depending on case definitions . The laboratory-based or clinical secondary attack ratios did not significantly differ across the intervention arms . Adherence to interventions was variable . Conclusions / Significance The secondary attack ratios were lower than anticipated , and lower than reported in other countries , perhaps due to differing patterns of susceptibility , lack of significant antigenic drift in circulating influenza virus strains recently , and /or issues related to the symptomatic recruitment design . Lessons learnt from this pilot have informed changes for the main study in 2008 . Trial Registration Clinical Trials.gov NCT00425893 HK Clinical Trials.com CONTEXT Data about the effectiveness of the surgical mask compared with the N95 respirator for protecting health care workers against influenza are sparse . Given the likelihood that N95 respirators will be in short supply during a p and emic and not available in many countries , knowing the effectiveness of the surgical mask is of public health importance . OBJECTIVE To compare the surgical mask with the N95 respirator in protecting health care workers against influenza . DESIGN , SETTING , AND PARTICIPANTS Noninferiority r and omized controlled trial of 446 nurses in emergency departments , medical units , and pediatric units in 8 tertiary care Ontario hospitals . INTERVENTION Assignment to either a fit-tested N95 respirator or a surgical mask when providing care to patients with febrile respiratory illness during the 2008 - 2009 influenza season . MAIN OUTCOME MEASURES The primary outcome was laboratory-confirmed influenza measured by polymerase chain reaction or a 4-fold rise in hemagglutinin titers . Effectiveness of the  surgical mask was assessed as noninferiority of the surgical mask compared with the N95 respirator . The criterion for noninferiority was met if the lower limit of the 95 % confidence interval ( CI ) for the reduction in incidence ( N95 respirator minus surgical group ) was greater than -9 % . RESULTS Between September 23 , 2008 , and December 8 , 2008 , 478 nurses were assessed for eligibility and 446 nurses were enrolled and r and omly assigned the intervention ; 225 were allocated to receive surgical masks and 221 to N95 respirators .  Influenza infection occurred in 50 nurses ( 23.6 % ) in the surgical mask group and in 48 ( 22.9 % ) in the N95 respirator group ( absolute risk difference , -0.73 % ; 95 % CI , -8.8 % to 7.3 % ; P = .86 ) , the lower confidence limit being inside the noninferiority limit of -9 % . CONCLUSION Among nurses in Ontario tertiary care hospitals , use of a surgical mask compared with an N95 respirator result ed in noninferior rates of laboratory-confirmed influenza . TRIAL REGISTRATION clinical trials.gov Identifier : 
    Output:
    
None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection .
Some evidence suggests that mask use is best undertaken as part of a package of personal protection especially h and hygiene .
The effectiveness of masks and respirators is likely linked to early , consistent and correct usage