Asthma and influenza vaccination.

A sthma appears to be a diathesis for morbidity related to influenza infection. Children and adults with asthma are at higher risk for influenza-related adverse health outcomes, including pneumonia, hospitalization for acute respiratory disease, and death.1–3 Because 5 to 10% of the US population has asthma, the potential public health impact of influenza infection on this vulnerable subgroup is enormous. The National Asthma Education and Prevention Program (NAEPP), coordinated by the National Heart, Lung, and Blood Institute, recently identified influenza vaccination as one of several “key clinical activities that should be considered as essential for quality asthma care.”4 The panel viewed influenza vaccination as so important that it was included among the “core set of 10 key clinical activities” that are aimed at reducing asthma morbidity and mortality. Given this recent emphasis on influenza vaccination for adults with asthma, the article by Ford and colleagues in the current issue of CHEST (see page 783) provides a timely snapshot of vaccine coverage for this high-risk target group. Using data from the population-based National Health Interview Survey from 1999 to 2001, the investigators found that only about one third of US adults with self-reported physician-diagnosed asthma received influenza vaccine during the past year. Although it appeared that a higher proportion of adults with asthma were being vaccinated than members of the general population (eg, 33.3% vs 25.9% in 2001), these data indicate a widespread failure of clinical care for asthma in the United States. There was also no evidence of improvement of influenza vaccination rates between 1999 and 2001. Why are so many adults with asthma not being vaccinated for influenza? In part, this appears to be a generic failure to achieve vaccination coverage. The Healthy People 2010 objectives indicate that 90% of adults aged 65 years should receive annual influenza vaccination, irrespective of chronic conditions.5 Based on the article by Ford and colleagues, the prevalence of vaccination is substantially lower among adults 70 years old, including both adults with (68.4 to 75.7%) and without asthma (65.0 to 68.6%). Consequently, the failure to vaccinate appears to be part of a general failure to deliver recommended health-care interventions. There are also some potential barriers to vaccination that may be specific to asthma. In particular, the safety of influenza vaccination in adults with asthma has been debated. A randomized controlled trial6 of influenza vaccine conducted with 262 asthma patients revealed a greater risk of asthma exacerbation, manifested by a 20% fall in peak expiratory flow rate, in the vaccine group compared to placebo. A larger-scale, randomized controlled trial7 of 2,032 adults with asthma, however, found no evidence of asthma exacerbation after influenza vaccination. Influenza vaccination had no adverse effect on a variety of safety outcomes: peak expiratory flow rate, oral corticosteroid use, bronchodilator rescue therapy, and unscheduled health-care utilization. Further strengthening the case for vaccine safety, a large multicenter cohort study8 of children with asthma found no evidence of adverse asthma health outcomes following influenza vaccination. Although influenza vaccine appears to be safe in patients with asthma, it remains possible that perception of vaccine safety still poses a barrier to vaccination, either among health-care providers or the general public. The efficacy of influenza vaccine for adults with asthma has also been questioned.9 A systematic review concluded that there was inadequate evidence to evaluate the efficacy of influenza vaccine for persons with asthma.9 In fact, there have been very few randomized controlled trials evaluating influenza vaccine among asthmatics. The existing trials are limited by small sample size, limited statistical power, and inconsistent quality.9 Perhaps the lack of specific randomized control trial data is another explanation for low influenza vaccination coverage. There is substantial indirect evidence, however, that influenza vaccine is beneficial for persons with asthma. The efficacy of influenza vaccination in healthy adults and elderly adults has been firmly established by randomized controlled trials.2,10–13 Moreover, epidemiologic studies14–16 support the strong protective effect of influenza vaccine in chilCHEST editorials