On July 10, 2014, CDC was informed by the California Department of Public Health and Office of Refugee Resettlement (ORR) about four unaccompanied male children aged 14-16 years with respiratory illnesses at Naval Base Ventura County, three of whom were hospitalized with pneumonia. Among the three patients with pneumonia, two were bacteremic with Streptococcus pneumoniae, ultimately determined to be serotype 5, one of whom also had laboratory-confirmed influenza B virus by polymerase chain reaction (PCR). The fourth patient, without pneumonia, had PCR-confirmed influenza A(H1N1)pdm09. Pneumococcal bacteremia is uncommon among U.S. adolescents, particularly serotype 5, with only three such cases identified in the past 10 years by CDC (2). In addition, influenza activity in the United States is typically lowest in the middle of summer, and Ventura County had no reports of an unusual increase in influenza activity in the community at the time. ORR asked CDC to investigate the scope of this apparent outbreak and implement measures to interrupt transmission. During July 6-19, 2014, CDC was informed of other clusters of hospitalized children with respiratory disease, increasing the total to 16 cases. Because of the concern that unaccompanied children were at increased risk for influenza and pneumococcal pneumonia in this outbreak setting and the clinically important interaction between influenza and pneumococcal infections (3), CDC recommended that all children residing in temporary or standard ORR shelters receive influenza vaccine and PCV13 in addition to routinely recommended vaccines. Approximately 2,000 children in four affected shelters were vaccinated during July 18-30 with PCV13 and with Food and Drug Administration-approved extended expiration date-specific lots of 2013-14 seasonal influenza vaccine, which includes influenza A(H1N1)pdm09 and influenza B viruses. The shelters reported no serious adverse events.