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Safe and effective vaccines will provide essential medical countermeasures to tackle the COVID-19 pandemic. Here, we assessed the safety, immunogenicity and efficacy of the intradermal delivery of INO-4800, a synthetic DNA vaccine candidate encoding the SARS-CoV-2 spike protein in the rhesus macaque model. Single and 2 dose vaccination regimens were evaluated. Vaccination induced both binding and neutralizing antibodies, along with IFN-γ-producing T cells against SARS-CoV-2. Upon administration of a high viral dose (5 × 106 pfu) via the intranasal and intratracheal routes we observed significantly reduced virus load in the lung and throat, in the vaccinated animals compared to controls. 2 doses of INO-4800 was associated with more robust vaccine-induced immune responses and improved viral protection. Importantly, histopathological examination of lung tissue provided no indication of vaccine-enhanced disease following SARS-CoV-2 challenge in INO-4800 immunized animals. This vaccine candidate is currently under clinical evaluation as a 2 dose regimen.

Original publication




Journal article



Publication Date





4885 - 4894


Public Health England (PHE), Porton Down, Salisbury, Wiltshire SP4 0JG, United Kingdom.


Animals, Macaca mulatta, Humans, Vaccines, DNA, Viral Vaccines, Antibodies, Viral, Antibodies, Neutralizing, Pandemics, Spike Glycoprotein, Coronavirus, COVID-19, SARS-CoV-2, COVID-19 Vaccines