The present study is designed to evaluate the efficacy and safety of a treatment with the recombinant vaccine BM32 during two consecutive grass pollen seasons. Efficacy evaluation will be performed on the basis of allergy symptoms and use of relief medication as well as based on immunological parameters. After patient assessment during a screening season, patients will be randomized to one of two doses of BM32 or placebo. Patients will receive three injections of BM32 pre-season and one post-season boost injection to maintain optimal allergen specific IgG responses. Outcome will be measured after both seasons individually.