Managed Care - October 2008 - (Page IS10) coverage achieved in 2004 was 43.2 percent (Lu 2008). A failure to meet vaccination goals in this group has the potential to increase influenza-related risk to patients and — particularly among the elderly and seriously ill — to increase influenza-related death as well. If caretakers are going to be true advocates for vaccination, it is incumbent on them to serve as role models by being vaccinated themselves. One might expect to see a reduction in the number of deaths in the older-than-65 age group, given their relatively high rate of vaccination, but this is not the case. Among all-cause deaths between 1990 and 2000, the total number of cases remained unabated, with about 90 percent of influenza deaths occurring in the elderly population (Thompson 2003, Thompson 2004). This may be due in part to senescence of the immune system and the resultant failure of the vaccine to provide optimal protection. On the other hand, low vaccination rates in the index group, which, as described below, is generally made up of school-aged children, may lead to poor disease control and rapid viral transmission throughout the community, affecting the frail elderly inordinately. 70% Vaccination coverage 60% 65+ 50% 40% 30% 20% 10% 0% 1989 1993 HCW 50–64 HR 18–49 HR 18–64 HH Pregnant women 1995 1998 2000 Survey year 2002 2004 FIGURE 1 Self-reported influenza vaccination coverage trends among adults by age groups and health care work status: 1989–2006 HCW=health care worker, HH=household contacts, HR=high-risk individuals. Reprinted from Vaccine, Volume 26, Lu, Bridges, Euler, Singleton, Influenza vaccination of recommended adult population, U.S., 1989–2005, 1786–1793, Copyright (2008), with permission from Elsevier. Community at large • Persons at increased risk of complications • Community-dwelling elderly • Social contacts of 1°, 2°, and 3° cases Family members of schoolchildren 3° • Working adults (parents) • Younger siblings • Other contacts Influenza virus transmission 2° More schoolchildren infected Children appear to play an important role in dissemination of the influenza virus, particularly during the early phase of a flu 1° Index case – immunologically naïve schoolchild epidemic when the index events first enter the community (Figure 2). According to FIGURE 2 Transmission of influenza Glezen (1982), school-age children represent a disproportionate number of inElveback LR, Fox JP, Ackerman E, et al. An influenza simulation model for immunization studies. Am J Epidemiol. 1976;103:152–165, by permission of Oxford University Press. fluenza cases in the early period of a flu epidemic, with a subsequent age shift in the population presenting for medical care. It was reported groups of classmates. Infected children then transport the that children 5 to 19 years of age represent more than 50 virus home to siblings, parents, and caretakers, and ultipercent of cases seen in the early phase but only 35 permately, to other contacts in the community. If children cent during the later phase of the outbreak. In contrast, are key transmitters of disease early in an epidemic, does the incidence of positive influenza cultures among adults focusing on immunization of the elderly and chroniaged 20 to 44 rose from 20.7 percent in the early phase cally ill population achieve the goal of deterring spread to 28.9 percent in the late phase and from 7.3 to 11.4 perof the disease? It might be more rational to prevent outcent among adults aged 45 or older in this same time breaks among school-age children to break the cycle of frame (Glezen 1982). progressive spread among susceptible individuals in the This has led some scientists to question the validity of community. the high-risk approach to influenza vaccination. School In fact, the advantage of vaccinating children for imand daycare settings are recognized incubators for viral proved control of influenza morbidity and mortality was spread due to children’s susceptibility to influenza infecsuggested as long ago as 1970. Investigators attempted to tion, high student density, poor understanding of hychange the course of the 1968 pandemic outbreak caused giene, and exposure to common items shared by large by influenza A/Hong Kong (H3N2) in Tecumseh, Mich., 10 MANAGED CARE / SUPPLEMENT
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