Safety and Efficacy of an Allergen Vaccine in Grass-Pollen Allergy

Inclusion Criteria: * 18 to 65 years of age * Mild to moderate seasonal allergic rhinoconjunctivitis due to sensitization against grass pollen as evident from history (≥ 2 years), and positive nasal provocation test (NPT) and positive skin prick test (SPT, wheal ≥ 3mm larger than diluent) to grass pollen extract * Female participants must meet one of the following criteria: No reproductive potential due to menopause (one year without menses, in case of doubts serum FSH will be determined and must be \>40 U/mL), hysterectomy, bilateral oophorectomy, or tubal ligation. Patient agrees to consistently practice an effective and accepted method of contraception throughout the duration of the study and for 1 additional months after the last immunization (hormone-based, or intrauterine device, or double barrier contraception, i.e. condom + diaphragm, condom or diaphragm + spermicidal gel or foam) * Written informed consent * Patient is willing and able to comply with all trial requirements Exclusion Criteria: * Additional allergies (seasonal or perennial) of which the symptoms overlap temporally with the screening and treatment period * Contraindication to Allergen Preparation * Contraindication for Nasal Provocation Test * Contraindication for Skin Prick Test * Actual significant obstructive pulmonary disorder (FEV1\< 70%) * Pharmacological treatment that could affect allergic sensitivity during the trial * Presence or history of significant cardiovascular, renal, pulmonary, endocrine, autoimmune, neurological, and psychiatric disease as judged by the investigator * Serum test positive for HIV, HBV, or HCV * Current diagnosis or history of malignancy; presence of suspicious lymphadenopathy or splenomegaly on physical examination * Pregnancy or lactation * Blood donation within 30 days before enrolment * History of abuse of alcohol or other recreational drugs * Specific immunotherapy against pollen allergy within the last two years * Intake of an investigational drug within three month before enrolment * Intake of contraindicated medicaments for SIT as Betablockers, ACE/ATII Inhibitors