Clinical Infectious Diseases (CID)
Volume 59 Issue 3 August 1, 2014
http://cid.oxfordjournals.org/content/current

School-Located Influenza Vaccination Decreases Laboratory-Confirmed Influenza and Improves School Attendance
Pia S. Pannaraj1,2, Hai-Lin Wang1, Hector Rivas3, Hilda Wiryawan1, Michael Smit1, Nicole Green3, Grace M. Aldrovandi1,2, Alvin Nelson El Amin4, and Laurene Mascola5
Author Affiliations
1Division of Infectious Diseases, Children’s Hospital Los Angeles
2Department of Pediatrics and Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California
3Public Health Laboratory
4Immunization Program
5Acute Communicable Disease Control, Los Angeles County Department of Public Health,
Abstract
Background.  School-located influenza vaccination (SLV) programs can efficiently immunize large numbers of school-aged children. We evaluated the impact of SLV on laboratory-confirmed influenza and absenteeism.
Methods. Active surveillance for influenza-like illness (ILI) was conducted on 4455 children in 4 SLV intervention and 4 control elementary schools (grades K–6) matched for sociodemographic characteristics during the 2010–2011 influenza season in Los Angeles County, California. Combined nose/throat swabs were collected from febrile children with ILI at presentation to the school nurse or during absenteeism.
Results. In SLV schools, 26.9%–46.6% of enrolled students received at least 1 dose of either inactivated or live attenuated influenza vaccine compared with 0.8%–4.3% in control schools. Polymerase chain reaction for respiratory viruses (PCR) was performed on 1021 specimens obtained from 898 children. Specimens were positive for influenza in 217 (21.3%), including 2009 H1N1 (30.9%), H3 (9.2%), and B (59.9%). Children attending SLV schools, regardless of vaccination status, were 30.8% (95% confidence interval, 10.1%–46.8%) less likely to acquire influenza compared with children at control schools. Unvaccinated children were indirectly protected in the school with nearly 50% vaccination coverage compared with control schools (influenza rate, 27.1 vs 60.0 per 1000 children; P = .023). Unvaccinated children missed more school days than vaccinated children (4.3 vs 2.8 days per 100 school days; P < .001).
Conclusions.  Vaccination of at least a quarter of the school population resulted in decreased influenza rates and improved school attendance. Herd immunity for unvaccinated children may occur in schools with vaccination coverage approaching 50%.