Vaccine use in school may reduce influenza burden

Issue: June 2007

Results from several studies showed that the use of FluMist in day care and school settings may help reduce the burden of seasonal influenza.

The results were presented at the Pediatric Academic Societies’ Annual Meeting in Toronto last month.

Additional data were presented from a study showing that increased vaccination rates may help prevent late-season influenza B outbreaks, as well as from a post-licensure safety analysis of FluMist (MedImmune) that showed that the vaccine was well-tolerated.

Day care study

Results from a previous study involving children aged 6 to 36 months attending day care centers showed that those children receiving FluMist experienced significantly fewer cases of influenza-like illness (Pediatrics. 2006;118:2298-2312).

New data estimated the economic effect of these clinical outcomes and noted a potential societal cost savings associated with vaccinating children against influenza. In the first year of the study, influenza vaccines saved about $5.47 per child, and in the second year of the study, the projected savings increased to almost $144 per child. The economic analysis also indicated that the significantly higher savings projected in the second year of the study were due in part to the substantially higher rate of influenza infection among the study population.

School-based vaccination

Data from a study of 15,000 children in 28 schools across four states (Maryland, Minnesota, Texas and Washington) showed that households of the 11 schools where children received FluMist reported statistically significant reductions in influenza-like illness, child doctors’ office visits, medications and work/school absenteeism in the peak flu week compared with the households of the 17 control schools where no influenza vaccinations were provided.

Researchers at the University of Maryland Medical Center conducted the study. All school households were asked to complete a survey on influenza-like illness symptoms, health care use and absenteeism from school or work during the predicted peak week for influenza epidemics. In a per-household economic analysis of the data, it was projected that costs related to immunizing children were largely recouped through reduced health care use and fewer work absences compared with those in the control schools.

Increasing vaccination rates

Researchers in central Texas reported that immunizing less than one-third of children participating in influenza intervention programs appears to have reduced Medically Attended Acute Respiratory Illness (MAARI) caused by influenza type B when compared with age-specific expected rates.

In the study, nearly 29% of children aged 5 to 19 years were vaccinated (73% with FluMist; 27% with the flu shot) during the 2005-2006 season, in which influenza outbreaks occurred in two waves, with type A predominating early in the season and type B in the later wave. Despite the higher pre-epidemic relative rate of MAARI in all age groups (particularly in children aged 5 to 17 years), there was a statistically reduced relative rate of MAARI in the B wave of the epidemic in two of the age groups and a suggestion of reduction in the others. There was no reduction of type A disease.

FluMist well-tolerated

Interim data were also presented from an ongoing post-marketing safety evaluation that has thus far revealed no unanticipated safety concerns in the nearly 45,000 FluMist recipients assessed to date. In the study, interim results were analyzed for the 2003-2004 and 2004-2005 seasons. Analyses were conducted for all ages combined and for three separate age subgroups: 5 to 8 years, 9 to 17 years and 18 to 49 years. The researchers analyzed rates of adverse events leading to visits to health care providers, emergency room use or hospitalizations through a review of medical use data on the vaccine recipients. The rates of events within the risk period (0 to 3 days or 0 to 21 days after vaccination, depending on the event) were then compared with a corresponding reference control period.

On Jan. 5, 2007, the FDA approved MedImmune’s supplemental Biologics Licensing Application for a refrigerated version of FluMist, which will be manufactured for the 2007-2008 influenza season.