Managed Care - October 2008 - (Page IS5) adults, fever of more than 100°F in children aged 2 to 6, and sore throat in adults (IIV 2008). The efficacy of influenza vaccination is related to both age and immune competency, and depends on a match with the circulating virus of the season. If the vaccine does not contain strains that reflect the circulating viral population, it may not protect against onset of influenza. When appropriately matched and used in healthy children and adults under age 65 years, the vaccine has been reported to prevent disease onset in 70 to 90 percent of treated subjects (Palache 1997). The immune-senescent elderly, however, achieve lower post-vaccination antibody titers, and, as a result, realize only 30 to 40 percent protection against onset of influenza-related illness (Blumberg 1996, Dorrell 1997, Nichol 1998). Elderly Prevention trends persons in nursing homes or chronic-care facilities benOver the years, many attempts have been made to efit from a 50 to 60 percent reduction in hospitalization suppress the spread of the influenza virus through such or pneumonia and an 80 percent decrease in death actions as isolating people, gargling with antiseptic, and (CDC 2001a, Patriarca 1985, Arden 1986). Current rewearing a mask. It was not until the development of insearch is focused on improving vaccines for the elderly, fluenza vaccine, however, that reliable protection against either by increasing the amount of antigen or by adding the spread of influenza could be achieved. an adjuvant compound that might stimulate the imToday’s influenza vaccine is the most effective means mune response to achieve better outcomes. to reduce the impact of influenza infection and virusA recent study examined the relative efficacy of LAIV related illness. The vaccine is a trivalent compound; that compared with TIV (Belshe 2007). In this head-to-head is, it contains the three strains of viruses, including H1N1 trial, approximately 8,000 children aged 6 months to 5 and H3N2 type A and the type B influenzas, commonly years were randomly assigned to vaccination with either found in the United States. There are two types of vacIM injection of TIV, or to the cold-adapted trivalent cines: a trivalent inactivated vaccine (TIV) and a liveLAIV (a refrigeration-stable formulation) nasal spray. attenuated influenza vaccine (LAIV). The former is made Children who developed influenza-like symptoms were from highly purified, egg-grown virus that is killed, and cultured to determine virus strain and titer. the hemagglutinin presented in the vaccine raises an Investigators observed a significant difference in the immune response (Kilbourne 1987). This vaccine is denumber of culture-confirmed cases of influenza that oclivered by intramuscular (IM) injection. The LAIV uses curred in subjects receiving LAIV versus TIV (153 vs. 338 live but weakened egg-grown virus delivered via a nasal cases, respectively; P<.001). The reduced rate of infection spray. Some inactivated viruses are approved for use in associated with LAIV was consistent across age groups children as young as 6 months, whereas the LAIV is used and for both antigenically well-matched influenza and starting at age 24 months through 49 years (Table). LAIV virus variants (Figure 3, page 6). In addition, there was is not approved for children younger than 24 months of a 50.6 percent greater reduction in rates of symptomatic age due to adverse events, primarily wheezing, that may influenza (P<.001), a 45.9 percent greater reduction in occur in a small percentage of patients. The most comlower respiratory infections (P=.046), and a 50.6 percent mon adverse reactions found to occur with the use of improvement in rates of acute otitis media associated LAIV are runny nose or nasal congestions in children and with LAIV versus TIV (P=.003). The broad coverage across multiple TABLE strains of influenza virus achieved with Current indications and contraindications for live-attenuated LAIV was confirmed in another study influenza vaccine (LAIV) vs. trivalent inactivated vaccine (TIV) in which the antibody response to a Nanchang strain vaccine protected LAIV TIV against multiple alternate viral strains, Indicated for ages 24 mo.–49 yr. Indicated for age older than 6 mos.* including the Sydney, Thessaloniki, Contraindications: egg allergy, Contraindications: egg allergy, Russian, and Johannesburg strains Guillain-Barré syndrome Guillain-Barré syndrome (Belshe 2000). LAIV provided better Not for recurrent wheezers immune protection and a broader Not for pregnant women range of activity than TIV. This broad * Different manufacturers have various ages indicated. protection advantage should enable viral RNA in as little as 15 minutes in the laboratory. In addition, rapid diagnostic tests are becoming more common and more reliable, allowing physicians to confirm the clinical diagnosis in the office setting. More than five rapid antigen-detection tests are available. Although modest in sensitivity (approximately 60 percent), these tests offer a rapid reading and, when positive, permit early initiation of antiviral therapy (CDC 2006). These tools are meeting with mixed reception among community physicians due to concerns about reliability and cost, but if nothing else, they will play a role in community influenza surveillance, particularly in less urban or academic settings. IMMUNIZATION STRATEGIES / MANAGED CARE 5
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