A self-amplifying mRNA vaccine developed by Arcturus Therapeutics has shown promising results during an ongoing phase 1/2/3 trial in Vietnam. The vaccine known as ARCT-154 offered 95 percent protection against severe Covid-19 and death, and 55 percent against COVID-19 infection, as per the company’s press release. A self-amplifying mRNA vaccine delivers RNA multiplies inside the body.
Meanwhile, mRNA vaccines developed by Pfizer/BioNTech and Moderna use messenger RNA that encodes the spike protein of the coronavirus. This means that the mRNA directs the cell to produce copies of the spike protein so that the immune system will recognise the spike if and when actual infection takes place, and mount a response. On the other hand, the self-amplifying mRNA vaccine encodes four extra proteins in addition to the vaccine antigen. This enables amplification of the original strand of RNA once inside the cell.
During the trial, the San Diego-based vaccine maker registered over 19,000 adult volunteers in Vietnam. Among these participants, there were individuals who are at higher risk of severe complications of COVID-19 disease. According to Arcturus Therapeutics, the Phase 3 placebo-controlled vaccine efficacy portion of this study enrolled over 16,000 participants.
During the trial, the analysis between 7 days and 56 days after completion of a two-dose vaccination series demonstrated 55 percent vaccine efficacy for protection against COVID-19, the company said in a statement. Moreover, these cases were detected during an outbreak in Vietnam when the Delta and Omicron variants were dominant.
The analysis of severe COVID-19 disease (including deaths) included 43 severe cases. The company also announced that 41 cases occurred in the placebo group and two in the vaccinated group, demonstrating vaccine efficacy of 95 percent. Meanwhile, nine deaths were reported in the placebo group, and one in the vaccinated group, whom the company described as an older age group participant who was also at increased risk of severe COVID-19.
The vaccine maker also informed that no cases of myocarditis or pericarditis were reported. However, the company conceded that the study does not have a large sample size to reliably observe these events given their extremely rare frequency of occurrence.