biostudies-literatureUnknown115Wong YC<h4>Background</h4>Inducing T cell responses by vaccines among elderly has been a long-standing challenge. There is a need for effective COVID-19 vaccines to boost waning immunity against emerging SARS-CoV-2 variants, especially for the elderly. This study investigated the safety and immunogenicity of a PD-1-enhanced COVID-19 DNA vaccine (ICCOV™), as a booster vaccine in healthy adults (aged 18-59 years) and elderly (aged 60-75 years).<h4>Methods</h4>This open-label, non-randomised Phase 2 study enrolled healthy participants aged 18-75 years who had previously been vaccinated with Sinovac CoronaVac, Pfizer-bioNTech Comirnaty vaccines, or both. Participants were stratified into four cohorts according to age, primary vaccination, and COVID-19 infection history, namely Adult-CoronaVac, Adult-EBioMedicine105699https://www.ebi.ac.uk/biostudies/studies/S-EPMC12143208biostudies-literatureAn open-label study on the safety and immunogenicity of a PD-1-enhanced DNA vaccine used as a T cell booster for COVID-19.PMC12143208Woo KFJin XCheng WYTai WKZhou RDu YNgai Hung IFZhang RHang Ho DHChen ZPolly Pang KPWang TWong YCfalseAn open-label study on the safety and immunogenicity of a PD-1-enhanced DNA vaccine used as a T cell booster for COVID-19.<h4>Background</h4>Inducing T cell responses by vaccines among elderly has been a long-standing challenge. There is a need for effective COVID-19 vaccines to boost waning immunity against emerging SARS-CoV-2 variants, especially for the elderly. This study investigated the safety and immunogenicity of a PD-1-enhanced COVID-19 DNA vaccine (ICCOV™), as a booster vaccine in healthy adults (aged 18-59 years) and elderly (aged 60-75 years).<h4>Methods</h4>This open-label, non-randomised Phase 2 study enrolled healthy participants aged 18-75 years who had previously been vaccinated with Sinovac CoronaVac, Pfizer-bioNTech Comirnaty vaccines, or both. Participants were stratified into four cohorts according to age, primary vaccination, and COVID-19 infection history, namely Adult-CoronaVac, Adult-2025-01-01T00:00:00Z2025 May2026-06-01T12:07:32.518Z2025-08-14T03:05:50.146ZS-EPMC121432084024549410.1016/j.ebiom.2025.105699