Managed Care - October 2008 - (Page IS11) by initiating a school-based effort aimed at universal immunization of schoolchildren Adrian (unvaccinated) 18 with an inactivated virus vaccine (Monto Tecumseh (vaccinated) 1970). The course of the pandemic out16 break was then compared with that seen in 14 neighboring Adrian, Mich., as well as in Flint and Lansing, Mich., where widespread 12 immunization was not carried out. The in10 vestigators achieved an overall rate of vaccination of 85.8 percent among students 8 enrolled in Tecumseh schools, which was 6 completed approximately 2 weeks before 4 the influenza virus was first isolated in the district. On follow-up, the investigators ob2 served a 26.7 percent overall effectiveness 0 rate in deterring respiratory illness during 0–4 5–9 10–14 15–19 20–29 30–39 40+ the pandemic. The reduction in respiratory Age groups (years) illness was reported in all age groups over FIGURE 3 Tecumseh, Mich.: Modification of influenza outbreak the course of the 10-week pandemic (Figure 3), indicating that protection was not Adapted with permission from Monto AS, et al. J Infect Dis. 1970;122:16–25 limited to the schoolchildren immunized, but also extended to adult members of the community aged children appears to be an effective way to slow the as well. progression of viral illness in the community (Monto Similar benefits during pandemic and epidemic in1970, Reichert 2001, Piedra 2005, Piedra 2007a). Our fluenza were ascribed to widespread immunization in data show that reaching 15 to 25 percent of children in several other investigations. An Australian study reported the community can yield up to an 18 percent reduction limited spread of H3N2 influenza in a small community in influenza-like illness cases in adults over age 35 (Piedra where individuals with chronic medical conditions, eld2005). A more recent study indicated that administering erly adults, and children between 1 and 5 years of age LAIV-T to children age 5 to 18 during the 2003–2004 inwere assigned to vaccination (Warburton 1972). In Japan, fluenza outbreak reduced the rate of influenza-positive a country that was an early proponent of widespread vaccultures by 37.3 percent and pneumonia and influenza cination of schoolchildren to control epidemic or seaevents by 50 percent, even though the outbreak arrived sonal influenza, administration of an inactivated inearly, was intense, and was caused by a drifted variant fluenza virus vaccine to 80 percent of schoolchildren (Piedra 2007a). Indirect protection against medically atwho were 7 to 15 years of age was found to prevent tended acute respiratory illness among adults aged 35 to between 37,000 and 49,000 excess deaths annually (Re44 and children aged 5 to 11 who were not vaccinated also ichert 2001). A mass vaccination campaign among Russwas observed. ian schoolchildren (aged 3 to 17 years) in two communities near Moscow led to a statistically significant Results of a community-based universal (P<.01) 3.4-fold reduction in cases of influenza-like illchild immunization program ness among more than 82,000 noninstitutionalized In 1998, a National Institutes of Health-sponsored adults older than age 60 when compared with results in clinical trial for widespread vaccination of children was the approximately 76,000 elderly subjects in two control initiated in central Texas as a means to cover as large a communities (Ghendon 2006). Vaccination with a trivabase as possible with influenza protection. The trial was lent live attenuated influenza vaccine (LAIV-T) among initiated by the Baylor College of Medicine, in Houston, 15 percent of children aged 1.5 to 18 enrolled in a cenin collaboration with the Scott & White Clinic, in Temtral Texas program reduced the rate of medically atple, Texas, one of the nation’s largest health care systended influenza-related illnesses by 8 to 18 percent in tems. Children were vaccinated with LAIV-T, adminisadults aged 35 or older (Piedra 2005, Piedra 2007a). tered by nasal spray, or the inactivated influenza vaccine The findings in all of these studies helped to establish (IIV-T), administered by intramuscular injection in the concept of “herd” immunity, or indirect protection, schools in several towns in central Texas. Healthy children in a community as a result of effective immunization of in the intervention cities received LAIV-T, whereas chilpreschool and school-age children — a large index group. dren with an at-risk condition received IIV-T. Age-eligiThe concept of herd protection has been documented, ble children in the comparison cities were not offered an and aggressive immunization of preschool and schoolinfluenza vaccine through the trial. Over the years, the Weekly mean rates of respiratory illness (%) IMMUNIZATION STRATEGIES / MANAGED CARE 11
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