Moderna has developed a more efficient version of its mRNA vaccine for COVID-19 that requires lower doses and has an extended shelf life when stored in a refrigerator. This improved vaccine, known as mRNA-1283, contains only two key parts of the virus’s spike protein instead of the entire protein.
Moderna recently announced that the vaccine has shown promising results in multiple clinical trials, and the company has completed enrollment for its late-stage clinical trial.
Studies have revealed that the most effective antibodies against the SARS-CoV-2 coronavirus bind to specific sites on the spike protein. Traditional vaccines contain the entire spike protein, which leads to the generation of antibodies against less effective parts of the protein.
To address this, Moderna’s vaccine codes for only the two key parts of the spike protein that contain the crucial binding sites. Animal tests have demonstrated that combining these two parts produces a stronger immune response compared to when they are separate.
The initial human trial of Moderna’s vaccine showed that even a tenth of the standard dose of their existing COVID-19 vaccine produced an antibody response comparable to a full dose of the original vaccine.
As a result, Moderna has chosen lower doses for subsequent clinical studies. However, the results of the phase 2 studies are yet to be released.
The shorter mRNAs in mRNA-1283 make it less prone to degradation, giving the vaccine a longer shelf life. When stored at refrigeration temperatures (2°C to 8°C or 36°F to 46°F), mRNA-1283 remains effective for a year compared to six months for the previous vaccine mRNA-1273.
The current version of mRNA-1283 being tested in the latest trial is a two-part vaccine. Half of the mRNA codes for the key sites from the original virus, while the other half targets the BA.4 and BA.5 omicron subvariants. If approved, the vaccine will be updated to target newer variants.
The latest mRNA booster shots, which have started rolling out, are designed to address the XBB.1.5 omicron subvariant that replaced BA.4 and BA.5. These booster shots no longer contain the original virus as studies indicated that it weakened the immune response.
The US has approved booster vaccines based on XBB.1.5 made by Moderna and Pfizer/BioNTech. The UK has approved the Pfizer/BioNTech booster vaccine. However, it is likely that people receiving boosters in the UK will be given stockpiled vaccines that target older variants.
Overall, Moderna’s enhanced mRNA vaccine offers improved efficacy at reduced doses and a longer shelf life. As ongoing trials progress, more data will become available to assess the vaccine’s safety and effectiveness against different COVID-19 variants.
