Initial report received from a literature on 06 February 2015. Abstract: The single best way to prevent influenza infection is to receive vaccination every year. Some organizations have a mandatory vaccination policy. Despite this, influenza outbreaks can occur in highly vaccinated populations, especially in confined settings. In February 2014, a total of 25 of the 102 personnel sought medical care because of influenza-like illness attributed to an influenza A (H3N2) virus antigenically similar to the H3N2 component of the 2013-14 vaccine. Among the personnel, 99% had received influenza vaccination, including 24 of 25 ill persons. Outbreak management included use of an antiviral medication, exclusion of the ill from the area for 48 hours, disinfection, hand washing, and cough etiquette. No personnel had onset of symptoms >6 days after the first person had symptoms. This influenza outbreak highlights the risk for an outbreak of H3N2 in a cohort of vaccinated and otherwise healthy young persons. The aforementioned information retrieved from full text article. 25 of 102 personnel sought medical care because of influenza-like illness (ILI). Nasal swab specimens were collected from each patient, and initial rapid influenza testing indicated 16 cases of influenza A. Ultimately, polymerase chain reaction (PCR) testing conducted by the Research Center determined that 20 specimens were influenza A, of which 18 were subtype H3N2. Two specimens could not be subtyped. The HA gene sequence of an outbreak isolate was 99% identical to strains circulating during the 2013-14 influenza season and antigenically similar to the H3N2 component of the 2013-14 influenza vaccine. At the time of the outbreak, 99% of the personnel had received influenza vaccine. Through the duration of the outbreak, the medical staff collaborated with Agency, higher-level authorities, and County Public Health Services to implement the outbreak response, which included disseminating outbreak information to surrounding agencies, disinfecting the area, sending home infected personnel, identifying family members at high risk, and providing antiviral medications and guidance. No personnel had onset of symptoms >6 days after the first person became ill. This outbreak highlights the risk for an H3N2 influenza outbreak among vaccinated and otherwise healthy young persons. Twenty personnel reported sick on February 10, one on February 11 and four more on February 12. Symptom onset dates were February 5-11. Two nasal swab specimens were taken from each ILI patient by staff members from the Research Center. Nasal swab specimens and influenza A and B rapid influenza tests were used for immediate influenza testing. The remaining nasal swab specimens were screened by the Research Center for influenza A and B using the CDC PCR assay (1), and DNA sequencing of the HA1 portion of the hemagglutinin gene was performed as previously described. All 25 personnel with ILI symptoms were otherwise healthy men aged 21-44 years. Rapid influenza testing indicated 16 cases of influenza A and nine negative results. Nasal swab specimens from 20 of the 25 ILI patients were positive by PCR for influenza A, with 18 specimens confirmed as A (H3) and two as A (untyped). Influenza A virus was isolated from seven of 11 nasal swab specimens selected for viral culture. These seven specimens had HA1 protein sequences that were identical to each other and differed from the H3N2 by 5 amino acid substitutions (N128A, R142G, N145S, P198S, and V347K). Sequence showed 99% homology to typical H3N2 strains circulating during the 2013-14 influenza season and were found to be antigenically similar to H3N2 (4). Ninety-nine of 102 personnel, 24 of the 25 with ILI symptoms, and 17 of 18 personnel were confirmed with H3N2 infection had received the 2013-14 influenza vaccine greater than or equal to 3 months before the outbreak. 16 were vaccinated via intradermal injection, eight via intranasal mist, and one had not received vaccination. In an effort to reduce spread and impact of disease, oseltamivir (75 mg twice a day for 5 days) was prescribed th each ILI patient who reported that symptoms had developed within 48 hours of their medical visit, regardless of their vaccination status and rapid influenza testing results. In addition to antiviral medication, rapid identification of the influenza outbreak, and immediate isolation of affected persons (personnel with ILI symptoms were sent to their homes for 48 hours), additional steps to control the outbreak were taken: thorough cleaning of spaces throughout the area by the crew and use of the area's public address system to instruct personnel to wash hands frequently, use hand sanitizer, cover their months when coughing, and report for medical evaluation if they were experiencing ILI symptoms. All patients experiencing ILI symptoms were required to wear a filtering facepiece respirator until 5 days after onset of symptoms. Cleaning of spaces was done by regularly disinfecting all commonly touch surfaces with disinfecting wipes and mopping all areas with an iodophor disinfectant diluted to 150 ppm of iodine. Upon medical review, the case was considered as serious due to important medical event: vaccination failure. List of documents held by sender: none.