The purpose of the study is to test the efficacy of a vaccine against house dust mite and/or cat allergy compared to placebo in adult patients.

Inclusion Criteria:

• Mild to moderate perennial allergic rhinoconjunctivitis due to hypersensitization towards house dust mite and/or cat allergens

Exclusion Criteria:

• Clinical relevant other allergies (perennial or seasonal) that could potentially interfere with the patient's study treatment schedule or assessments.
• Use of any concomitant medication that could affect the patient's study treatment response or assessment results.
• Any clinically relevant concomitant disease as judged by the investigator.
• Pregnancy or female planning to become pregnant during the study.