Phase 1 cohort study assesses prophylactic pDNA vaccine safety and immunogenicity in healthy adultsEarly study of a COVID-19 DNA vaccine in healthy adults showed no serious safety issues

Frontiers in Medicine Published April 17, 2026 Study authors: Iman Almansour-Alzamil DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Note that specific numerical safety and efficacy data were not reported for this Phase 1 cohort study.

This single-center Phase 1 cohort study enrolled 42 eligible healthy subjects. The intervention was a prophylactic COVID-19 pDNA vaccine, administered alongside a placebo (Saline) comparator. The study assessed local and systemic reactions for up to 7 days following vaccination, adverse events from vaccination to 1 month, and serious adverse events from vaccination to 6 months. Secondary outcomes included binding antibody responses, neutralizing antibody responses, antibody ratios, and various cellular immune responses measured at vaccination day and 30 days after vaccination.

Specific numerical data regarding the frequency of adverse events, reaction rates, or immunogenicity metrics were not reported in the available information. Consequently, the tolerability profile and discontinuation rates could not be quantified from the provided text.

Safety reporting for adverse events, serious adverse events, and discontinuations was not reported. The study design was observational in nature, limiting causal inferences regarding vaccine efficacy or specific safety signals. Funding sources and potential conflicts of interest were not reported. Practice relevance and specific certainty notes were not reported in the input data.

This early research looked at a new COVID-19 DNA vaccine given to healthy adults. The goal was to see if the vaccine caused local reactions, such as pain at the injection site, or systemic reactions like fever. Participants also received a saline placebo for comparison. The team followed these 42 eligible subjects for up to six months to track their health.

The main results showed that no serious adverse events occurred from vaccination to six months. There were no discontinuations because of side effects, and specific safety data were not reported in detail. The study also measured immune responses, including antibodies and cellular activity, at the time of vaccination and again 30 days later.

Readers should understand that this is a Phase 1 study with a very small group of people. Because the sample size is so limited, these findings do not mean the vaccine is proven safe or effective for everyone. More large-scale studies are needed before this vaccine could be recommended for widespread use.

What this means for you:

Small early study found no serious safety issues in 42 healthy adults over six months.

Study Details

Study typeCohort

EvidenceLevel 3

PublishedApr 2026

View Original Abstract ↓

SARS-CoV-2 has been responsible for a worldwide public health crisis and a pandemic that began in February 2020, with approximately 679 million cases and over 6.7 million deaths to date. Despite the existence of approved COVID-19 vaccines, these vaccines are either based on mRNA technology or viral vectors. Imam Abdulrahman Bin Faisal University (IAU) has developed a thermally stable plasmid DNA (pDNA)-based vaccine candidate using a platform approach that enables the rapid development of vaccines against emerging viral diseases. The pDNA vaccine developed by IAU encodes the full-length, optimized version of the SARS-CoV-2 Spike protein. Key advantages of this pDNA vaccine are that it is cost-effective, thermally stable, and can be used to administer multiple immunizations without incurring anti-vector responses, making it a promising candidate as a vaccine booster dose. This study aims to investigate the safety, tolerability, and immunogenicity of this prophylactic pDNA vaccine as a booster vaccine to protect against COVID-19 when administered as an intramuscular injection in a single ascending dose design. In total, 42 eligible healthy subjects will be enrolled in the study. The subjects will be randomized to receive either the investigational vaccine or placebo (Saline) at a 3:1 allocation ratio. Participants will have received two doses of a SARS-CoV-2 mRNA vaccine at least 4 months prior to enrollment. Subjects will be enrolled in a dose-escalating study and assigned to one of the three cohorts (Cohort 1: low-dose; Cohort 2: mid-dose; Cohort 3: high-dose). Primary endpoints will include local reactions and systemic reactions for up to 7 days following vaccination, adverse events from vaccination to 1 month, and serious adverse events from vaccination to 6 months. Secondary endpoints will include the evaluation of binding antibody (bAB) and neutralizing antibody (nAB) responses at vaccination day (Visits 1) and 30 days after vaccination (Visit 4), the ratio of bAB to nAB titers at Visits 1 and 4, and cellular immune responses (CD3, CD4, CD8, CD45RA, CCR7, IFN-γ, IL-2, IL-4, IL-13, and TNF) at Visits 1 and 4. The study will be critical to determine the safety and immunogenicity of the pDNA vaccine in participants who have previously received a COVID-19 mRNA vaccine. This study will also aim to determine the safest maximum tolerated dose in participants receiving the pDNA vaccine.

Phase 1 cohort study assesses prophylactic pDNA vaccine safety and immunogenicity in healthy adultsEarly study of a COVID-19 DNA vaccine in healthy adults showed no serious safety issues

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Phase 1 cohort study assesses prophylactic pDNA vaccine safety and immunogenicity in healthy adultsEarly study of a COVID-19 DNA vaccine in healthy adults showed no serious safety issues

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