Follow-up of Study AN004T to Assess the Persistence of AllerT Efficacy During the 2nd to 4th Season After Treatment

Inclusion Criteria: 1. Any subject having been randomized in the AN004T trial and had received at least one injection 2. Any subject having been informed and provided signed consent for participating in the trial and willing to follow all planned trial assessments Exclusion Criteria: 1. Any subject having received specific immunotherapy against birch pollen or a tree pollen mix including birch pollen at any time since AN004T and before Visit 1 2. Any subject intending to travel during the birch pollen season outside of the birch pollination area for more than 7 consecutive days 3. Any subject unable or unwilling to record allergy symptoms and medications daily during the following birch pollen season using an electronic diary device 4. Any subject not covered by medical insurance 5. Any subject having received immunosuppressive medication within 4 weeks prior to inclusion, or planned to be used during the trial period 6. Any subject having received systemic or local antihistamines, oral or inhaled corticosteroids or under anti depressant medication with antihistamine effect within 2 weeks prior to inclusion 7. Any subject having used any investigational or non-registered drug, vaccine, or medical device within 4 weeks prior to inclusion, or planned to use such treatments during the trial period