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School-based influenza vaccination program linked to decreased school absences, hospitalization
SAN FRANCISCO — An elementary school-located influenza vaccination program increased vaccination and decreased school absences and hospitalizations related to influenza in students, according to research presented at IDWeek.
Jade Benjamin-Chung, PhD, an epidemiologist at the University of California, Berkeley, studied the impact of a program that delivered the inactivated influenza vaccine in 2016 to 2017 to schools in a large, urban school district in Oakland, California.
In her prospective study, Benjamin-Chung measured parental reports of student influenza vaccinations in surveys for 44 schools per district (n = 6,070) in 2017. She also gathered data on absences from the school districts and influenza hospitalization during the time of the immunization program. Benjamin-Chung estimated difference in differences (DIDs) in absence rates during influenza season by using generalized linear models and adjusting for month, race and grade.
Benjamin-Chung reported there was a 56.7% vaccination coverage in the control district and 63.9% in the program school district, for a difference of 7.2% (95% CI, 3.6%-10.8%). Almost a quarter of the students (24%) in the program schools were vaccinated at school. Absences and illnesses were lower in the schools participating in the program (5.40 absences and 3.01 illness-related absences per 100 days) compared with the control school sites (6.68 absences and 3.60 illness-related absences per 100 days).
Benjamin-Chung reported that DIDs in absence rates were statistically significant for absences related to illness. She also reported that the risk ratio for influenza hospitalization for all ages in program districts compared with control districts was 0.65 (95% CI, 0.55-0.88) and 0.71 (95% CI, 0.57-0.80) for adults aged 65 years or older. Risk ratios could not be reported for elementary school-aged children, because hospitalization was rare among those students, Benjamin-Chung reported.
The vaccination program produced “an indirect effect on hospitalization in elderly and non-elementary aged groups," she wrote. – by Bruce Thiel
Reference:
Benjamin-Chung J. Abstract LB20. Presented at: IDWeek; Oct. 3-7, 2018; San Francisco.
Disclosure: Benjamin-Chung reports no relevant financial disclosures.
Perspective
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As epidemiologists (and parents) know, school-age children are often infected with influenza and respiratory viruses and serve as amplifiers of infection in the community. Benjamin-Chung and colleagues set out to ask if reducing influenza in this group through school-located influenza vaccination programs could reduce influenza and its complications in the community. Their data is the strongest yet to support this hypothesis.
They examined the impact of school-located influenza vaccination program with IIV in 2016 to 2017 in the Oakland Unified School District. They carefully chose the year as vaccine effectiveness varies by season. In 2016 to 2017, CDC estimated that IIV was 53% effective. There were no randomized control schools – a potential limitation. However, they carefully matched the individual Oakland schools to schools in another demographically similar district. This resulted in intervention and control schools closely matched for age, race, gender and socioeconomic status.
Vaccination coverage was 64% in the schools with school-located immunization, 7% higher than the control schools. The investigators found significant reductions between the schools in illness-associated absenteeism in the schools during the influenza season, as well as the peak week of flu transmission. More importantly, using surveillance data for influenza-associated hospitalization they observed significant reductions in non-elementary school children and in older adults, suggesting significant “herd immunity.” No difference was seen in absenteeism or hospitalization in years where the vaccine used in schools had poor effectiveness.
Mathematical modeling has predicted that immunizing 70% of school-age children will lead to a herd effect. This study suggests a benefit despite lower coverage and modest vaccine efficacy. Other studies have consistently shown that school-located flu immunization programs can improve coverage for a variety of vaccines. Until now, data on the community impact have been limited. This study provides strong support for expanding school-located immunization programs and for continuing to study the indirect impact on those at highest risk of influenza complications.