A streamlined version of Moderna’s vaccine that targets only key parts of the spike protein of the SARS-CoV-2 coronavirus is being trialled in humans
By Michael Le Page
13 September 2023
Moderna’s original RNA vaccine for covid-19 was first rolled out in 2021
Dinendra Haria/Getty Images
Moderna has created a streamlined version of its mRNA vaccine against covid-19 that is effective at lower doses and lasts twice as long when stored in a refrigerator. The vaccine includes only two key parts of the spike protein of the virus, instead of the entire protein.
The improved vaccine, called mRNA-1283, has “demonstrated encouraging results in multiple clinical studies” and the company has now completed enrollment of its late-stage clinical trial, Moderna announced on 13 September.
Numerous studies have shown that the most effective antibodies against the SARS-CoV-2 coronavirus bind to one of two key sites on the spike protein that protrudes from the virus’s surface. One of these sites, for instance, is the part of the protein that attaches to human cells and helps the virus get inside, so antibodies that bind to this site block this process.
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However, almost all existing covid-19 vaccines consist of the entire spike protein, prompting the immune system to generate antibodies against other parts of the protein, many of which aren’t effective.
So, Moderna has created a vaccine that consists of an mRNA coding for just the two parts of the protein containing the key sites. Animal tests showed that linking these two parts produced a better response than when they were separate, according to a paper in Science Translational Medicine, also released on 13 September.
The first human trial of this vaccine revealed that even people given a tenth of what is the standard dose for Moderna’s existing covid-19 vaccine, called mRNA-1273, produced an antibody response that was just as strong as a full dose of the original vaccine, according to a preprint released in October 2022.