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Table 1 Summary of objectives and outcome measures

From: Evaluation of the safety and immunogenicity of different COVID-19 vaccine combinations in healthy individuals: study protocol for a randomized, subject-blinded, controlled phase 3 trial [PRIBIVAC]

Objectives

Outcome measures

Timepoint(s)

Primary objective

 To determine whether heterologous prime-boost-boost COVID-19 vaccine regimens lead to non-inferior humoral immunity compared with homologous prime-boost-boost vaccine regimen against wildtype SARS-CoV-2 and/or 1≥ VOC

Level of SARS-CoV-2 anti-spike immunoglobulins

Day 28

Secondary objectives

 To determine whether heterologous prime-boost-boost COVID-19 vaccine regimens lead to non-inferior humoral and cellular immunity compared with homologous prime-boost-boost vaccine regimen against wildtype SARS-CoV-2 and/or 1≥ VOC

Level of SARS-CoV-2 anti-spike immunoglobulins

Level of SARS-CoV-2 neutralizing antibodies

Quantitative T cell responses to spike proteins

Days 1, 7, 180, 360

Days 1, 7, 28, 180, 360

Days 1, 7, 28, 180, 360

 To assess the reactogenicity and safety of heterologous and homologous prime-boost-boost COVID-19 vaccine schedules

Solicited local and systemic reaction

Changes from baseline in laboratory safety measures

Unsolicited adverse events (AEs)

Serious adverse events (SAEs), AEs of special interest (e.g., myocarditis, pericarditis), medically attended AEs

Day 7

Day 7

Day 28

Throughout the study

Exploratory objectives

 To determine whether vaccine efficacy differs between heterologous and homologous prime-boost-boost regimens

PCR-confirmed COVID-19 infections as recognized by the Ministry of Health, Singapore

Throughout the study

To determine whether the administered mRNA vaccine (control group and intervention group 1 only) can be detected in the blood at ~1 week post-vaccination

qRT-PCR using primers targeting the sequence of the mRNA for SARS-CoV-2 spike protein

Day 7