Immunogenicity and Safety of a Single 0.5 mL Dose of Inflexal V With a 0.25 mL 2-dose Regimen of Inflexal V

• Inflexal V (Biological): vaccination with Inflexal V 0.25 mL administered twice, 4 weeks apart
• Inflexal V (Biological): Inflexal V 0.5 mL administrated once only

Primary outcomes

• Immunogenicity of a Single Full (0.5 mL) Dose and a 0.25 mL 2-dose Regimen of Inflexal V, Using the EMA Guideline for the Re-registration of the Seasonal Influenza Vaccine in Adults (Aged ≥18 to ≤60 Years) as Reference [This assesment was done for immunogenicity data collected at Day 29 after completion of designated vaccination regimen]: Seroprotection rate
• Immunogenicity of a Single Full (0.5 mL) Dose and a 0.25 mL 2-dose Regimen of Inflexal V, Using the EMA Guideline for the Re-registration of the Seasonal Influenza Vaccine in Adults (Aged ≥18 to ≤60 Years) as Reference [This assesment was done for immunogenicity data collected at Day 29 after completion of designated vaccination regimen]: Seroconversion rate
• Immunogenicity of a Single Full (0.5 mL) Dose and a 0.25 mL 2-dose Regimen of Inflexal V, Using the EMA Guideline for the Re-registration of the Seasonal Influenza Vaccine in Adults (Aged ≥18 to ≤60 Years) as Reference [This assesment was done for immunogenicity data collected at Day 29 after completion of designated vaccination regimen]: GMT-fold increase - calculated as the GMT on Day 22 divided by the baseline GMT value

Secondary outcomes

• Number of Participants With Local and Systemic Adverse Events as a Measure of Safety and Tolerability [Solicited local and systemic AEs were collected from Day 1 (day of vaccination) to Day 4 inclusive using a subject diary]

Sex: All, ages: 6 Months to 35 Months, accepts healthy volunteers

Inclusion Criteria:

* Healthy male and female children
* Aged ≥6 to <36 months on Day 1
* Born at a gestational age ≥37 weeks
* Written informed consent
* No previous influenza vaccination

Exclusion Criteria:

* Acute respiratory infection or other acute disease
* Acute febrile illness (≥38.0 °C)
* Past vaccination with an influenza vaccine, including vaccination against the influenza strain A/California/7/2009 (H1N1)-like virus
* Laboratory-confirmed infection with any influenza strain, including the pandemic influenza strain H1N1 (A/California/7/2009 (H1N1)-like virus)
* Known hypersensitivity to any vaccine component
* Known history of egg protein allergy or severe atopy
* Known blood coagulation disorder
* Chronic (longer than 14 days) administration of immunosuppressants or other immune-modifying drugs within 6 months before the first dose of the study vaccine, incl. oral corticosteroids in dosages of ≥0.5 mg/kg/d prednisolone or equivalent for ≥14 days (inhaled or topical steroids are allowed)
* Known immunodeficiency (including leukemia, cancer, HIV seropositivity)
* Investigational medicinal product received in the past 3 months (90 days)
* Treatment with immunoglobulins or blood transfusion(s) received in the past 3 months (90 days)
* Vaccination with the MMR vaccine in the past 4 weeks, or planned within the study period
* Participation in another clinical trial
* Child or legal charge of the investigator or an employee at the study site, or living in the same household as the investigator/employee and/or dependent on the investigator/employee
* Suspected non-compliance

Participant flow

Outcome results

• Immunogenicity of a Single Full (0.5 mL) Dose and a 0.25 mL 2-dose Regimen of Inflexal V, Using the EMA Guideline for the Re-registration of the Seasonal Influenza Vaccine in Adults (Aged ≥18 to ≤60 Years) as Reference (Primary), Number, percentage subjects: Inflexal V 0.25 mL x 2 99.0 (94.4 to 100); Inflexal V 0.5 mL x 1 98.0 (92.9 to 99.8)
• Number of Participants With Local and Systemic Adverse Events as a Measure of Safety and Tolerability (Secondary), Number, participants: Inflexal V 0.25 mL x 2 - After 1st Vaccination 51; Inflexal V 0.25 mL x 2 - After 2nd Vaccination 48; Inflexal V 0.5 mL x 1 49
• Immunogenicity of a Single Full (0.5 mL) Dose and a 0.25 mL 2-dose Regimen of Inflexal V, Using the EMA Guideline for the Re-registration of the Seasonal Influenza Vaccine in Adults (Aged ≥18 to ≤60 Years) as Reference (Primary), Number, percentage subjects: Inflexal V 0.25 mL x 2 92.9 (85.1 to 97.3); Inflexal V 0.5 mL x 1 95.5 (88.8 to 98.7)
• Immunogenicity of a Single Full (0.5 mL) Dose and a 0.25 mL 2-dose Regimen of Inflexal V, Using the EMA Guideline for the Re-registration of the Seasonal Influenza Vaccine in Adults (Aged ≥18 to ≤60 Years) as Reference (Primary), Number, Fold (ratio): Inflexal V 0.25 mL x 2 25.5 (21.3 to 30.5); Inflexal V 0.5 mL x 1 19.6 (16.9 to 22.7)

Adverse events

Time frame: Any AE occurring within 1 month (minimum 28 days) following vaccine administration was recorded. Any SAE occurring from study start up to 6 months (at least 180 days) following vaccine administration was recorded.

Serious adverse events by term

Other adverse events by term

• Nicola Principi, Prof Dr, Principal investigator, Institute of Paediatrics, University of Milan, Fondazione IRCCS "Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena", Via Commenda 9, 20122, Milano, Italy
• Gian Vincenzo Zuccotti, Prof Dr, Principal investigator, Department of Pediatrics, Department of Clinical Sciences, Università di Milano, L. Sacco Hospital, 74, Via GB Grassi,