Section VII
12
MMWR
demonstrate that persons with asthma benefit from vaccination (134). However, a meta-analysis that examined effectiveness among persons with chronic obstructive pulmonary disease identified evidence of benefit from vaccination (135). Immunocompromised Persons TIV produces adequate antibody concentrations against influenza among vaccinated HIV-infected persons who have minimal AIDS-related symptoms and normal or near-normal CD4+ T-lymphocyte cell counts (136–138). Among persons who have advanced HIV disease and low CD4+ T-lymphocyte cell counts, TIV might not induce protective antibody titers (138,139); a second dose of vaccine does not improve the immune response in these persons (139,140). A randomized, placebo-controlled trial determined that TIV was highly effective in preventing symptomatic, laboratory-confirmed influenza virus infection among HIV-infected persons with a mean of 400 CD4+ T-lymphocyte cells/mm3; however, a limited number of persons with CD4+ T-lymphocyte cell counts of <200 were included in that study (140). A nonrandomized study of HIV-infected persons determined that influenza vaccination was most effective among persons with >100 CD4+ cells and among those with <30,000 viral copies of HIV type-1/mL (53). On the basis of certain limited studies, immunogenicity for persons with solid organ transplants varies according to transplant type. Among persons with kidney or heart transplants, the proportion who developed seroprotective antibody concentrations was similar or slightly reduced compared with healthy persons (141–143). However, a study among persons with liver transplants indicated reduced immunologic responses to influenza vaccination (144–146), especially if vaccination occurred within the 4 months after the transplant procedure (144). Pregnant Women and neonates Pregnant women have protective levels of anti-influenza antibodies after vaccination (147,148). Passive transfer of anti-influenza antibodies that might provide protection from vaccinated women to neonates has been reported (147,149– 151). A retrospective, clinic-based study conducted during 1998–2003 documented a nonsignificant trend toward fewer episodes of MAARI during one influenza season among vaccinated pregnant women compared with unvaccinated pregnant women and substantially fewer episodes of MAARI during the peak influenza season (148). However, a retrospective study conducted during 1997–2002 that used clinical records data did not indicate a reduction in ILI among vaccinated pregnant women or their infants (152). In another study conducted
VII / 114
July 31, 2009
during 1995–2001, medical visits for respiratory illness among the infants were not substantially reduced (153). One randomized controlled trial conducted in Bangladesh that provided vaccination to pregnant women during the third trimester demonstrated a 29% reduction in respiratory illness with fever and a 36% reduction in respiratory illness with fever among their infants during the first 6 months after birth. In addition, infants born to vaccinated women had a 63% reduction in laboratory-confirmed influenza illness during the first 6 months of life (154). All women in this trial breastfed their infants (mean duration: 14 weeks). older Adults Adults aged >65 years typically have a diminished immune response to influenza vaccination compared with young healthy adults, suggesting that immunity might be of shorter duration (although still extending through one influenza season) (155,156). However, a review of the published literature concluded that no clear evidence existed that immunity declined more rapidly in the elderly (157), and additional vaccine doses during the same season do not increase the antibody response (118,120). Infections among the vaccinated elderly might be associated with an age-related reduction in ability to respond to vaccination rather than reduced duration of immunity (127,128). One prospective cohort study found that immunogenicity among hospitalized persons who were either aged >65 years or who were aged 18–64 years and had one or more chronic medical conditions was similar compared with outpatients (158). The only randomized controlled trial among communitydwelling persons aged >60 years reported a vaccine efficacy of 58% (CI = 26%–77%) against laboratory-confirmed influenza illness during a season when the vaccine strains were considered to be well-matched to circulating strains (159). Additional information from this trial published separately indicated that efficacy among those aged >70 years was 57% (CI = -36%– 87%), similar to younger persons. However, few persons aged >75 years participated in this study, and the wide confidence interval for the estimate of efficacy among participants aged >70 years included 0 (160). Influenza vaccine effectiveness in preventing MAARI among the elderly in nursing homes has been estimated at 20%–40% (161,162), and reported outbreaks among well-vaccinated nursing home populations have suggested that vaccination might not have any significant effectiveness when circulating strains are drifted from vaccine strains (163,164). In contrast, some studies have indicated that vaccination can be up to 80% effective in preventing influenzarelated death (161,165–167). Among elderly persons not living in nursing homes or similar long-term–care facilities, influenza
VA Influenza Manual 2009 / 2010