RT Journal
A1 Finkelstein Y, Schechter T, Freedman SB
T1 SUrgical masks vs n95 respirators for preventing influenza
JF JAMA
JO JAMA
YR 2010
FD March 10
VO 303
IS 10
SP 937
OP 939
DO 10.1001/jama.2010.195
UL http://dx.doi.org/10.1001/jama.2010.195
AB 
There is no proof that the participating nurses contracted influenza due to failure of the assigned respiratory barrier. It is likely that a significant proportion contracted influenza outside of their clinical duties, which likely represent less than 25% of total weekly hours. Although household exposures were reported, uncontrolled exposures undoubtedly occurred as part of daily activities. Such exposures are especially relevant in the context of the current pandemic. Therefore, attributing infection as solely due to barrier failure is inappropriate in the context of nonusage outside of work. These nonclinical exposures were likely similar between groups and may have contributed to the finding of noninferiority.