The return of the mixed respiratory bacterial vaccine

Background: Orally or sublingually administered lysates of mixed respiratory pathogenic bacteria have been used in Europe, Asia, and other parts of the world, but not the United States, since the mid 1950s, first to prevent recurrent respiratory tract infections, later to prevent wheezing and asthma exacerbations associated with respiratory infections, and, more recently, for the treatment of allergic rhinitis. The apparent success of this treatment contrasts with the negative experience of treating with injections of similar mixed respiratory bacterial vaccines (MRBV or BV) to prevent asthma exacerbations associated with respiratory infections that was once common practice but abandoned ∼50 years ago. Methods: Textbooks and articles on the use of injected BVs to prevent asthma exacerbations associated with respiratory infections were reviewed, including a number of, randomized, double-blind, placebo controlled (RDBPC) studies the results of which were predominantly negative that contributed to the abandonment of this treatment. Also reviewed were more recent articles from Europe and China, which report both clinical and immunologic support for the use of the orally and sublingually administered mixed respiratory bacterial lysates (MRBL or BL). Results: A review of five RDBPC studies of the parenteral use of BVs for prevention of asthma exacerbations conducted by leading international allergists in the 1950s and 1960s showed, in a combined 532 patients, an overall reduction of asthma attacks by 4.9% over placebo. However, in five studies in 1126 patients of oral or sublingual treatment with BLs, the reduction in respiratory infections, wheezing episodes, and asthma exacerbations was 42.6% over placebo. Conclusion: Reported results with oral and sublingual BLs are far superior to the historical performance of injected BVs. Possible reasons for this difference are discussed, but none is clearly responsible for the difference in clinical results.