Intradermal influenza vaccination may result in better efficacy when compare to intramuscular vaccination.

This is a prospective, randomized, single centre trial in the Queen Mary Hospital. We aim to recruit 400 subjects [with a minimum of 50 subjects per group] who would be qualified for the Hospital Authority (HA)/ Centre for Health Protection (CHP) Mass Vaccination Program for 2010/2011 TIV. These patients include all elderly at the age of 65 or above and all adult patients at the age of 21 or above with chronic illness (or healthcare workers). Subjects will be randomly assigned into 4 groups: Group 1 (ID1) to receive a single low-dose intradermal injection of 2010/2011 TIV, with a microneedle device. Group 2 (ID2) to receive a single higher low-dose intradermal injection of 2010/2011 TIV with a microneedle device. Group 3 (IM15) to receive a single full-dose (15ug) standard 2010/2011 TIV delivered intramuscularly by conventional needle. Group 4 (INT) to receive a single low-dose intradermal injection of 2010/2011 TIV, with Intanza® needle. The 2010/2011 TIV used will be Fluzone®, Sanofi-Pasteur for group 3 and Intanza®, Sanofi-Pasteur for group 1,2 and 4.

Inclusion Criteria:

• All participants qualified for the HA/ CHP Mass Vaccination Program for TIV 2010/2011 seasonal influenza as stated above: including all elderly at the age of 65 or above and all adult patients at the age of 21 or above that are either healthcare workers or that have a chronic illness including hypertension, diabetes mellitus, ischemic heart disease, cerebrovascular disease, thyroid disease and chronic renal failure.
• All patients give written informed consent.
• Subjects must be available to complete the study and comply with study procedures.

Exclusion Criteria:

• Clinically significant immune-related diseases, significant recent co-morbidities and pregnant volunteers.
• History or any illness that might interfere with the results of the study or pose additional risk to the subjects due to participation in the study
• Have a known allergy to eggs or other components of the Study Vaccines (including gelatin, formaldehyde, octoxinol, thimerosal, and chicken protein), or history of any anaphylaxis, serious vaccine reactions, to any excipients.
• Have immunosuppression as a result of an underlying illness or treatment, or use of anticancer chemotherapy or radiation therapy (cytotoxic) within the preceding 36 months.
• Have an active neoplastic disease or a history of any hematologic malignancy.
• Have known active human immunodeficiency virus (HIV), Hepatitis B, or Hepatitis C infection or autoimmune hepatitis and cirrhosis.
• History of progressive or severe neurological disorders or Guillain-Barré Syndrome.