Patient selection and administration of aeroallergen vaccines

Allergic rhinitis and asthma are common throughout the world and continue to increase in prevalence. These disorders continue to have significant morbidity and mortality despite increased understanding of disease pathogenesis and development of new effective medications for treatment. Immunotherapy is indicated for many of these patients, but risk–benefit ratios should be considered during patient selection. The World Health Organization published a 1998 position paper summarizing the current status and future directions of immunotherapy. 71 Still, among physicians, "opinions vary from complete rejection of the method for any purpose (a view held by many who are not allergists) to almost ritual use in any patient with upper or lower respiratory tract symptoms that are even vaguely allergic." 43 For conditions such as allergic rhinitis and asthma, immunotherapy is adjunctive to proper medical therapy, unlike in persons who have experienced a life-threatening stinging insect reaction where immunotherapy is curative. When aeroallergen immunotherapy in asthma was reviewed in a meta-analysis of 20 randomized, double-blind, placebo-controlled trials, there was significant improvement in asthmatic symptoms and a reduction in medication requirements, but only modest improvements in lung function for treated patients. 1 This analysis, however, included only two studies of children, and most studies did not use standardized vaccines. The limited number of double-blind, placebo-controlled trials of specific allergen immunotherapy involving large numbers of patients has limited its widespread acceptance; however, numerous studies have shown that immunotherapy for allergic respiratory disease significantly lessens the severity of symptoms and medication requirements. There are no controlled trials demonstrating benefit in subjects treated with immunotherapy for atopic dermatitis. The benefits of immunotherapy are specific for the antigen used for treatment. It is difficult to study large numbers of patients who are allergic to a single allergen, as most patients have multiple allergen sensitivities. Most studies that employed symptom diaries to judge efficacy have found that treatment with a single allergenic vaccine provides incomplete relief of symptoms. 43 This may be due either to the limitations of the treatment itself or to the failure to immunize with all relevant allergens. Clinical observations during a period of natural allergen exposure cannot distinguish between these two possibilities; however, a controlled trial of multiple allergen immunotherapy in asthmatic children failed to show treatment benefit. 2 Allergen avoidance remains the primary treatment for allergic disease and is essential in most cases of animal allergen sensitivity or occupational exposure. Most common aeroallergens, however, cannot be avoided completely, and exposure is almost inevitable, especially for patients with multiple sensitivities. Studies suggest that specific immunotherapy may prevent new allergic sensitization 16 or even the onset of asthma. 30 Currently, studies are underway in Europe to address the question of whether treatment of allergic rhinitis with immunotherapy can prevent the development of allergic asthma.