Inclusion Criteria:

• Mentally competent adults, who have signed an informed consent form after having received a detailed explanation of the study protocol.
• Male or female subjects over 18 years who are either healthy or have a stable medical condition.
• Able to understand and comply with all study procedures and to complete study diaries
• Individuals who can be contacted throughout the study and are available for all study visits
• Females should either be using secure contraceptive precautions including a) the oral contraceptive pill, b) condom/barrier contraception c) partner has had a vasectomy, d) be surgically sterilised, or e) post- (defined as at least two years since the last menstrual period)

Exclusion Criteria:

• Any clinically significant concurrent illness or unstable medical condition including: malignant tumours, autoimmune illnesses (including rheumatoid arthritis), acute or progressive renal or hepatic pathology, chronic obstructive pulmonary disease requiring oxygen therapy, and any active neurological disorder.
• Individuals with a history of anaphylaxis or serious reactions to vaccines; hypersensitivity to eggs, chicken protein, chicken feathers, influenzal viral protein, neomycin or polymixin, or products containing mercury.
• Persons with known immunosuppressive disease or who use systemic immunosuppressive drugs or other drugs listed in section 8 of the British National Formulary (BNF) or chloroquine, gold or penicillamine or other drugs listed in section 10.1.3 of the BNF to suppress a chronic disease process, or have received in the last 6 months radiotherapy or chemotherapy.
• Subjects who are at high risk of developing illnesses of the immune system.
• Individuals who are taking immunostimulant therapy or interferon
• Individuals who have received blood products or immunoglobulins parenterally during the preceding three months.
• Women should not be pregnant or lactating.
• Women who refuse to use a reliable contraceptive method throughout the study
• Known or suspected drug abuse.
• Individuals who have received another vaccine or experimental (investigational) drug in the preceding 4 weeks.
• Individuals who have previously received H9N2 vaccine
• Unable to lead an independent life either physically or mentally
• Regularly drink more than 40 units of alcohol weekly
• Individuals who have had acute respiratory pathology or infections requiring systemic antibiotic or antiviral therapy during the preceding 7 days (chronic antibiotic therapy for prevention of urinary tract infections is acceptable).
• Individuals who had a temperature over 38 degrees C in the preceding 3 days.
• Individuals who, in the opinion of the investigator, have conditions that might complicate interpretation of the study results.