The purpose of this study was to evaluate a single dose of FluBlok in terms of safety, efficacy and effectiveness in prevention of influenza and influenza-like illness and assess clinical lot-to-lot consistency in manufacturing by evaluating and comparing the immunogenicity of three different lots of FluBlok in a subset of participants.

All currently licensed influenza vaccines in the United States were produced in embryonated hen's eggs. There were several well-recognized disadvantages to the use of eggs as the substrate for influenza vaccine. Eggs required specialized manufacturing facilities and could be difficult to scale up rapidly in response to an emerging need such as a pandemic. It was usually necessary to adapt candidate vaccine viruses for high-yield growth in eggs, a process that could be time consuming, was not always successful, and could select receptor variants that might have suboptimal immunogenicity. In addition, agricultural diseases that affected chicken flocks, and that might be an important issue in a pandemic due to an avian influenza virus strain, could easily disrupt the supply of eggs for vaccine manufacturing. Therefore, development of alternative substrates for influenza vaccine production had been identified as a high-priority objective.

One potential alternative method for production of influenza vaccine was expression of the influenza virus hemagglutinin (HA) using recombinant deoxyribonucleic acid (DNA) techniques. This alternative avoided dependence on eggs and was very efficient because of the high levels of protein expression under the control of the baculovirus polyhedrin promoter.

Inclusion Criteria:

• Healthy adult aged 18-49 years.
• Provided informed consent prior to any study procedures.
• Able to comply with all study procedures.
• Available for follow-up for the duration of the influenza season.
• Women of child-bearing potential must have had a negative urine pregnancy test at the time of randomization and must be willing to use an adequate form of contraception (includes abstinence, condom with spermicide, licensed hormonal contraceptive, intrauterine device [IUD], monogamous relationship with a vasectomized partner) during the course of the study.

Exclusion Criteria:

• Long-term use of oral steroids, parenteral steroids, or high-dose inhaled steroids (greater than [>] 800 mcg/day of beclomethasone dipropionate or equivalent) within the preceding 6 months (Nasal and topical steroids were allowed).
• Presence of high-risk conditions or other characteristics were considered to be indication for influenza vaccination, as defined by the Advisory Committee on Immunization Practices.
• Acute febrile illness (defined as having a temperature greater than or equal to [>=]100 degrees Fahrenheit) or upper respiratory tract illness within 72 hours of vaccination. Participants with acute febrile illness were rescheduled after fever resolved.
• Use of experimental vaccines or any influenza vaccine other than FluBlOk after May 31st 2007 for the 2008 Southern Hemisphere or 2007 to 2008 Northern hemisphere epidemic seasons.
• Immunosuppression as a result of an underlying illness or treatment, or used anticancer chemotherapy or radiation therapy within the preceding 36 months.
• Any malignancy diagnosed or treated actively during the past five (5) years, with two (2) exceptions. Participant with any history of lymphoproliferative disorder were excluded. However, participants with a history of localized non-melanotic skin cancer were eligible.
• Receipt of any other licensed vaccines within 2 weeks (for inactivated vaccines) or 4 weeks (for live vaccines) prior to enrollment in this study.
• Receipt of an experimental agent (vaccine, drug, biologic, device, blood product or medication) within 1 month prior to enrollment in this study, or expected to receive an experimental agent during study period.
• Receipt of parenteral immunoglobulin or other blood product within the three months prior to study vaccination.
• Major psychiatric diagnosis including schizophrenia, bipolar disease or other major depression, or any diagnosis of dementia or associated concomitant medications (e.g., Aricept) used for treating dementia.
• Known active human immunodeficiency virus, hepatitis B, or hepatitis C infection.
• History of alcohol or drug abuse in the last 5 years.
• Not available for three or more consecutive weeks during flu surveillance period.
• Any acute or chronic condition that, in the opinion of the investigator, would render vaccination unsafe or interfere with the evaluation of responses or render the participant unable to meet the requirements of the protocol.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org