Compare Dose Regimens of AllerT, in Adults With Allergic Rhino-Conjunctivitis to Birch Pollen Studied in EEC

Inclusion Criteria: * Minimum two-year history of moderate to severe rhino-conjunctivitis on exposure to birch pollen with a need to take symptomatic medications (antihistamine, steroid) during pollen season, prior to study enrollment. * Sensitivity to birch tree pollen confirmed at Screening by both of the following criteria: * Positive Skin Prick Test (SPT) to birch pollen extract (wheal ≥ 3 mm than the negative control). Negative control must be ≤ 2 mm. * Positive specific IgE CAP test for Bet v 1 (≥ 0.7 kU/L). * A qualifying score in at least one of the two Baseline EEC Challenges: at least one diary card of 12/24 or greater for Total Rhinoconjunctivitis Symptom Score (TRSS) as well as either one diary card 6/12 or greater for Total Nasal Symptom Score (TNSS) or Total Ocular Symptom Score (TOSS). Exclusion Criteria: * Positive SPT to AllerT (wheal ≥ 3 mm than the negative control). * Received specific immunotherapy against: * Any allergen within three years before the Screening visit. * Birch tree pollen or a tree pollen mix including birch pollen at any time before the Screening visit. * Clinically significant symptoms due to allergens other than birch pollen during the EEC challenge periods (eg, perennial allergies, allergies to other pollens with overlapping allergy seasons during the EEC periods). * Persistent un-controlled asthma; subjects with a Forced Expiratory Volume (FEV1) lower than 80% of their predicted value and/or subjects under chronic treatment fo…