Studies that analyzed the effectiveness of facemasks as a means of protection from virus contamination
Suess et al. The role of facemasks and hand hygiene in the prevention of influenza transmission in households: results from a cluster randomised trial; Berlin, Germany, 2009-2011. BMC Infectious Diseases 2012, 12:26. http://www.biomedcentral.com/1471-2334/12/26
Main results / conclusions: Data analysis showed that interventions (facemask or facemask + hands hygiene) did not result in statistically significant reductions in secondary infections among household members.
MacIntyre et al. … Neil Ferguson. Face Mask Use and Control of Respiratory Virus Transmission in Households. Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 15, No. 2, February 2009
Main results/conclusions: The analysis of randomized data showed no statistically significant difference between the treated and control groups. The authors suggest that the use of facemasks is probably not an efficient way to control seasonal respiratory diseases, but they still recommend their use.
Aiello et al. Mask Use, Hand Hygiene, and Seasonal Influenza-Like Illness among Young Adults: A Randomized Intervention Trial. The Journal of Infectious Diseases 2010; 201:491–8 2010. DOI: 10.1086/650396
Main results / conclusions: Significant reductions in the spread of infections were observed in weeks 4-6 in the “facemask + hand hygiene” group compared to the control group. The use of facemasks only did not cause a statistically significant reduction. However, there was no significant reduction in the cumulative transmission rate in either group.
Cowling et al. Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households. A Cluster Randomized Trial. Ann Intern Med. 2009;151:437-446.
Main results / conclusions: There was a reduction in the transmission of influenza with both interventions (hand hygiene or facial mask + hand hygiene). The odds ratio in the “hand hygiene”
group was 0.46, while the odds ratio in the “facial mask + hand hygiene group” was 0.33.
Simmerman et al. Findings from a household randomized controlled trial of hand washing and face masks to reduce influenza transmission in Bangkok, Thailand. 2011 Influenza and Other Respiratory Viruses, 5, 256–267
Main results / conclusions: Influenza transmission was not reduced by interventions (hand hygiene or face mask + hand hygiene)
Larson et al. Impact of Non-Pharmaceutical Interventions on URIs and Influenza in Crowded, Urban Households. Public Health Reports / March–April 2010 / Volume 125.
Main results / conclusions: Individuasl were allocated in each of the following three groups: “hand hygiene”, “hand hygiene + facial masks” and “instruction on the prevention of respiratory diseases”. The latter served as a control. The main conclusion was that there was no significant difference between the groups regarding the number of respiratory infections during the 19 months of follow-up of those involved in the experiment. There was a reduction in secondary infections in the group “hand hygiene + face masks” compared to the control (odds ratio = 0.82), that is, the risk of contracting the disease of an infected family member was 1.2 times lower in this group). However, adherence to the use of masks was very low.
Aiello AE, Perez V, Coulborn RM, Davis BM, Uddin M, et al. (2012) Facemasks, Hand Hygiene, and Influenza among Young Adults: A Randomized Intervention Trial. PLoS ONE 7(1): e29744. doi:10.1371/journal.pone.0029744
Main results / conclusions: When compared to the control, both intervention groups (face mask or facial mask + hand hygiene) showed cumulative reductions in influenza rates during the study period, but the results did not reach statistical significance. The “face mask + hand hygiene” group presented a 4-fold lower risk compared to the control group, which was not observed in the “face mask” group only.
Studies that analyzed the effectiveness of facemasks wore by index cases
Canini L, Andréoletti L, Ferrari P, D’Angelo R, Blanchon T, Lemaitre M, et al. (2010) Surgical Mask to Prevent Influenza Transmission in Households: A Cluster Randomized Trial. PLoS ONE 5(11): e13998. https://doi.org/10.1371/journal.pone.0013998
Main results / conclusions: There was no evidence that suggeste/d the effectiveness of wearing masks by sick patients, despite the good adherence of individuals participating in this study.
MacIntyre CR, Zhang Y, Chughtai AA, et al. Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness. BMJ Open 2016;6:e012330. doi:10.1136/bmjopen-2016- 012330
Main results / conclusions: The relative risks of the masked group were lower than that of the control group when the infection was assessed by symptomatology, but nonexistent when the assessment was done by laboratory tests. In addition, there was not statistically significant differences in any case.
Barasheed, Osamah, et al. “Pilot randomised controlled trial to test effectiveness of facemasks in preventing influenza-like illness transmission among Australian Hajj pilgrims in 2011.” Infectious Disorders-Drug Targets (Formerly Current Drug Targets-Infectious Disorders) 14.2 (2014): 110-116.
Main results / conclusions: The masked group infected 31% of the individuals accommodated in the same tent, while in the tents where no masks were used by the infected, that number rose to 53%. However, these data were based on reports from the study participants, who reported their symptoms. When the secondary infected individuals were tested for the presence of 5 types of viruses that could potentially cause these symptoms, the difference between the groups disappeared.