A Phase 2, Comparative, Randomised, Adaptive Trial to Evaluate the safety and immunogenicity of one dose of COMIRNATY in subjects that had received one dose of VAXZEVRIA.

INTERVENTION: Trade Name: COMIRNATY. Concentrado para dispersión inyectable Product Name: Comirnaty Pharmaceutical Form: Dispersion for injection CONDITION: Covid‐19 Vaccination Therapeutic area: Diseases [C] ‐ Virus Diseases [C02] SECONDARY OUTCOME: Secondary end point(s): Secondary immunogenicity end‐point:; ? Serological response to vaccination (antibodies against SARS‐Cov2 spike protein) as measured by immunoassay, 28 days after the boost dose.; ? SARS‐CoV‐2 neutralization as measured by virus neutralization assay, 14 and 28 days after the boost dose.; ? Serological response to vaccination (antibodies against SARS‐Cov2 spike protein) as measured by immunoassay at 3, 6 and 12months after the boost dose.; ? Neutralizing antibody titers at 3, 6 and 12 months after the boost dose.; Secondary efficacy end‐points:; ? The number of participants with molecularly confirmed COVID‐19.; ? Presence and severity of COVID‐19 signs and symptoms as measured by Symptoms of; Infection with Coronavirus‐19 (SIC). Timepoint(s) of evaluation of this end point: Secondary immunogenicity end‐point:; Serological response to vaccination (antibodies against SARS‐Cov2 spike protein) as measured by immunoassay, 28 days after the boost dose.; SARS‐CoV‐2 neutralization as measured by virus neutralization assay, 14 and 28 days after the boost dose.; Serological response to vaccination (antibodies against SARS‐Cov2 spike protein) as measured by immunoassay at 3, 6 and 12months after the boost dose.; Neutralizing antibody titers at 3, 6 and 12 months after the boost dose. INCLUSION CRITERIA: 1. Adult subjects (18 years old) having received a previous single dose of VAXZEVRIA vaccination between 8 and 12 weeks before the screening visit. 2. Subjects in good health or stable clinical situation. 3. Subject providing informed consent to participate in the trial. Are the trial subjects under 18? no Number of subjects for this age range: F.1.2 Adults (18‐64 years) yes F.1.2.1 Number of subjects for this age range 300 F.1.3 Elderly (>=65 years) yes F.1.3.1 Number of subjects for this age range 300 PRIMARY OUTCOME: Main Objective: Primary Immunogenicity Objective: To assess the humoral immune response against SARS‐Cov‐2, 14 days after a vaccination with COMIRNATY in subjects that received a previous single dose of VAXZEVRIA, as compared with dosing, in SARS‐Cov2 seronegative adults.; Primary Safety Objectives:To evaluate the safety of a dose of COMIRNATY in subjects that received a previous single dose of VAXZEVRIA in subject aged more than 18 years and in good health or stable clinical situation that have received a previous single dose of VAXZEVRIA.; A stratification will be made taking into account: site of vaccination, sex and age. Subjects will be randomized in a proportion of 2:1. If primary analysis at 14 days confirms the starting hypothesis, subjects randomized to no vaccination will be crossed to receive a dose of COMINARTY. In case the primary analysis does not confirm the starting hypothesis, subjects will be followed without administration of COMINARTY. Primary end point(s): Primary immunogenicity end‐point:; Serological response to vaccination (antibodies against SARS‐Cov2 spike protein) as measured by immunoassay, 14 days after the boost dose.; Primary safety end‐points:; Solicited local and systemic adverse events (AEs) for 7 days after vaccine; Unsolicited local and systemic adverse events (AEs) for 28 days after vaccine; Serious adverse events (SAEs) throughout the study (from randomization until end of the study).; Medically‐attended adverse events (MAAEs) from the day of vaccination until 6 months after the last vaccination. Secondary Objective: Secondary immunogenicity objectives:; To assess the humoral immune response against SARS‐Cov‐2, 28 days after a vaccination with COMIRNATY in subjects that received a previous single dose of VAXZEVRIA.; To assess the long‐term (up to 1 year) humoral immune response against SARS‐Cov‐2 of a dose of COMIRNATY in subjects that received a previous single dose of VAXZEVRIA.; Exploratory objective:Evaluate the relationship between the immune response measured as NAV (Neutralizing antibodies) and antibodies against SARS‐Cov2 spike protein measured by immunoassay.; To assess the humoral immune response against viral variants of SARS‐Cov‐2, 14 and 28 days after a dose of COMIRNATY in subjects that received a previous single dose of VAXZEVRIA.; Secondary efficacy objectives: To assess the occurrence of symptomatic molecularly confirmed COVID‐19 and severity of COVID‐19 signs and symptoms after the administration of a dose of COMIRNATY in subjects that received a prior single dose of VAXZEVRIA. Timepoint(s) of evaluation of this end point: Primary immunogenicity end‐point:14 days after the boost dose.; Primary safety end‐points:; Solicited local and systemic adverse events (AEs) for 7 days after vaccine; Unsolicited local and systemic adverse events (AEs) for 28 days after vaccine; Serious adverse events (SAEs) throughout the study (from randomization until end of the study).; Medically‐attended adverse events (MAAEs) from the day of vaccination until 6 months after the last vaccination.