School-located influenza vaccination decreases laboratory-confirmed influenza and improves school attendance.
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%.
Division of Infectious Diseases, Children's Hospital Los Angeles Department of Pediatrics and Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California.
Pia S
PS
Pannaraj
Division of Infectious Diseases, Children's Hospital Los Angeles.
Hai-Lin
HL
Wang
Public Health Laboratory.
Hector
H
Rivas
Division of Infectious Diseases, Children's Hospital Los Angeles.
Hilda
H
Wiryawan
Division of Infectious Diseases, Children's Hospital Los Angeles.
Michael
M
Smit
Public Health Laboratory.
Nicole
N
Green
Division of Infectious Diseases, Children's Hospital Los Angeles Department of Pediatrics and Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California.
Grace M
GM
Aldrovandi
Immunization Program.
Alvin Nelson
AN
El Amin
Acute Communicable Disease Control, Los Angeles County Department of Public Health, California.
Laurene
L
Mascola
D000041:Absenteeism; D000293:Adolescent; D002140:California / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D012574:Schools; D013334:Students / Q000706:statistics & numerical data; D014611:Vaccination; D014613:Vaccines, Attenuated
D007252:Influenza Vaccines; D014613:Vaccines, Attenuated
herd immunity; influenza; influenza vaccine; school-located influenza vaccination