A Study to Evaluate the Immunogenicity and Safety of Seqirus Quadrivalent Influenza Vaccine (QIV) in a Pediatric Population 6 Months Through 59 Months of Age.

A Phase 3, Randomized, Multicenter, Observer-blinded, Noninferiority Study to Evaluate the Immunogenicity and Safety of a Quadrivalent Inactivated Influenza Virus Vaccine (Seqirus QIV) With a US-licensed Quadrivalent Inactivated Comparator Influenza Virus Vaccine (Comparator QIV) in a Pediatric Population 6 Months Through 59 Months of Age

This is a study to assess the immune (antibody) response and safety of a Seqirus split virion, inactivated Quadrivalent Influenza Vaccine (Seqirus QIV), in comparison with a US licensed 2016/2017 Quadrivalent Influenza Vaccine (comparator QIV) in a healthy pediatric population 6 months through 59 months of age.

Inclusion Criteria:

• Male or female subject 6 months through to 59 months of age at the time of first vaccination and born between 36 and 42 weeks of gestation;
• Parent or legally acceptable representative able to provide written informed consent and be willing and able to adhere to all protocol requirements including blood draws.
• Subject is in generally good health as per the Investigator's medical judgment

Exclusion Criteria:

• History of allergic reactions to egg proteins or any components of the Study Vaccines;
• History of serious adverse reactions to any influenza vaccines;
• History of Guillain-Barré syndrome or other demyelinating disease such as encephalomyelitis and transverse myelitis;
• History of licensed or investigational influenza vaccination in the last 6 months;
• Clinical signs of active infection and/or an axillary temperature of ≥ 99.5°F / (≥ 37.5 °C) on the day of vaccination or within 48 hours preceding vaccination.
• Current or recent, acute or chronic medical conditions that in the opinion of the Investigator are clinically significant and/or unstable
• History of any seizures, with the exception of a single febrile seizure;
• Self-reported or known seropositivity suggestive of acute or chronic viral infection for human immunodeficiency virus, hepatitis B or hepatitis C;
• Known or suspected congenital or acquired immunosuppressive conditions;
• Current or recent immunosuppressive or immunomodulatory therapy
• Current or medical history of malignant neoplasms;
• Administration of immunoglobulin and/or any blood products within the previous 90 days preceding the administration of the Study Vaccine or planned administration during the study;
• Participation in a clinical trial or use of an investigational compound within 28 days prior to or 28 days after receiving the Study Vaccine, or plans to enter a study during this period;
• Vaccination with a licensed vaccine 21 days (for live or inactivated vaccines) prior to receiving the Study Vaccine, or plans to receive any licensed vaccine prior to the Study Exit Visit.
• Medical conditions or treatment contraindicating intramuscular vaccination due to increased risk of bleeding.
• Family members of the employees of the Investigator or study center with direct involvement in the study, or with other clinical studies under the direction of that Investigator or study center.