The primary goal of this study is to assess the safety of 4 different dosages of purified monovalent surface antigen (SA) influenza A/H9N2 virus vaccine with or without MF59 adjuvant and administered intramuscularly to ambulatory adults. The hypothesis is that all dosage levels of adjuvanted and nonadjuvanted vaccine will be well tolerated. The primary objective of this project is to evaluate the safety of 4 dosage levels of monovalent surface antigen (SA) influenza A/H9N2 virus vaccine given with or without MF59 adjuvant. The primary endpoint is the frequency and severity of solicited local and systemic adverse events in each vaccine dosage level group. The secondary objective of this project is to determine the immunogenicity of 4 dosage levels of monovalent surface antigen (SA) influenza A/H9N2 virus vaccine given with or without MF59 adjuvant. The secondary endpoints include the following: the proportions of subjects in each vaccine dosage group that achieve a serum HAI titer of at least 1:32 one month after the second vaccination; the geometric mean titer (GMT) of serum HAI antibody against the influenza A/H9N2 virus one month after the second vaccination; the rates of significant increases in titer between pre- and post-immunization serum samples (defined as seroconversion-i.e., increase in titer from <1:4 pre-immunization to at least 1:8 after vaccination, or 4-fold or greater increase in titer between pre- and post-immunization samples) 28 days after each vaccination (days 28 and 56); and the proportion of subjects with a 4-fold or greater increase in percent HA-specific antibody in nasal wash specimens for each vaccine group. The study will be a double-blind evaluation of 4 dosage levels of study vaccine. The 4 dosage levels to be tested are 3.75-, 7.5-, 15-, and 30-mcg of HA of the vaccine strain with and without MF59 adjuvant. Because all dosage levels are lower than the total hemagglutinin content of the FLUAD® vaccine used in Europe, subjects will be enrolled into all dosage and adjuvant groups concurrently using a randomized, double-blind study design. Ninety-six persons 18-34 years of age will be enrolled. A single lot of monovalent inactivated SA influenza A/H9N2 vaccine will be used throughout the trial. All injections will be administered in a 0.5-mL volume into the deltoid muscle. Screening and safety laboratory examinations will be assessed before the first dose and 7 days after each vaccination. Assessments for reactogenicity will be done for at least 20 minutes after each vaccination, in the clinic 2 and 7 days after each inoculation, via diary card for seven days after each vaccination, and via phone or other contact at 7 months after the first vaccination for any serious adverse events during the entire study period. Serum and nasal wash samples collected on days 0, 28, and 56 will be used to measure immunogenicity of the vaccine preparation. Participants will be involved in study related procedures for up to 8 months.