(1) Objectives: to assess the immunogenicity and safety of Flupak seasonal influenza vaccine with 3 × 15 µg HA active ingredient content in healthy adults between 18 to 65 years old; to assess the immunogenicity of hemagglutinin of vaccine strains (the titer of anti HA antibody responses) in healthy human by serology testing (hemagglutinin inhibition) of blood taken at day 21 to 28 after intervention; to assess Flupak vaccine tolerability (incidence of adverse reactions) in humans.
(2) Design: phase 2; double blind, controlled, randomization and single center clinical study of Flupak trivalent seasonal influenza vaccine to assess safety, immunogenicity and Flupak vaccine tolerability (incidence of adverse reactions) of the study. Sample size is 100 healthy adults between 18 to 65 years old.
(3) Setting and conduct: after physical examinations and blood sampling at day 0, injection will be done on 3 groups of participants (groups are selected randomly); intervention group1 (35 members): 0.5 ml of influenza Flupak vaccine is injected; intervention group 2 (35 members): 0.5 ml of influenza Vaxigrip vaccine is injected; control group (30 members): 0.5 ml of placebo (injectable phosphate buffered saline) is injected; injection for all 3 groups is administered at one side into the deltoid muscle with a deep intramuscular injection; blood samples from cubital vein to test for specific antibody against influenza viruses by serology testing will be taken at day 0 and at day 21 to 28 after intervention, the titer of antibody in total mean titer of participants must increase in comparison with the titer before vaccination.
(4) Inclusion criteria: healthy adults between 18 to 65 years old, both sexes;
Exclusion Criteria: known allergy to eggs or other components of vaccine (such as: formaldehyde and octoxinol-9); history of Guillain-Barre syndrome; pregnancy; breast feeding; positive pregnancy test prior to vaccination; immunosuppressive therapy in preceding 36 months; active neoplasm; psychiatric illness.
(5)Intervention:
Intervention group1 (35 members): 0.5 ml of influenza Flupak vaccine is injected; intervention group 2 (35 members): 0.5 ml of influenza Vaxigrip vaccine is injected.
(6) Control:
Control group (30 members): 0.5 ml of placebo (injectable phosphate buffered saline) is injected.
(7) Main outcomes:
Primary outcome: systemic reactions such as fever higher than 38 degree for 24 hours or more, headache, malaise; swelling and inflammation at the injection site with diameter more than 50 mm which lasts more than 3 days; blood samples from cubital vein to test for specific antibody against influenza viruses by serology testing will be taken at day 0 and at day 21 to 28 after intervention;
Secondary outcomes: local reaction at the injection site such as pain, edema, redness, swelling, warmth; clinically significant changes in physical status and vital signs such as skin, mucous membranes, blood pressure, heart rate, lungs, abdomen, liver, nervous system and anaphylactic shock.