Background: In a previous controlled study, we demonstrated that preseasonal grass pollen immunotherapy for 3 years was effective in children. Moreover, a significant clinical benefit could still be observed 6 years after discontinuation of specific immunotherapy (SIT). In the current study, we examined the same group of patients again to investigate whether there is a prolonged benefit 12 years after SIT is stopped.
Methods: Twenty-two patients with previous SIT (from 1989 through 1991) or standardized seasonal pharmacotherapy only were prospectively followed during the grass pollen season of 2003. Primary end points were symptom score, medication use, and combined symptom and medication score. In addition, skin prick test reactivity, development of new sensitizations, and prevalence of seasonal asthma were evaluated.
Results: Total hay fever symptom score (P < 0.03), use of medication (P < 0.05), and combined symptom and medication score (P < 0.03) remained lower in patients with previous SIT when compared with the control group. Decreased immediate skin response to grass pollen returned 12 years after cessation of SIT. The percentage of new sensitization, however, continued to be significantly smaller in patients with previous SIT (58%) compared with the controls (100%, P < 0.05). There was a tendency for lower prevalence of seasonal asthma in the post-SIT group (P = 0.08).
Conclusion: This prospective controlled prolonged follow-up study demonstrates the ongoing clinical benefit 12 years after discontinuation of SIT. Furthermore, the reduction in onset of new sensitization, which was found 6 years after discontinuation of SIT, is sustained 6 years later.