A COVID-19 booster targeting two versions of the coronavirus in one shot offered stronger and broader protection than the current booster, which targets only one version, according to clinical trial results released this week by vaccine maker Moderna.
The results are preliminary and have not been peer reviewed or published in a scientific journal. But Moderna touted the findings as evidence that bivalent or multivalent vaccines—those that target two or more versions of the virus in a single shot—are the way forward for COVID-19 boosters.
Moderna and other vaccine makers are on a mission to develop boosters that could restore the once extraordinarily high levels of protection that mRNA-based COVID-19 vaccines initially provided, while also protecting against future variants. The first-generation mRNA vaccines were all designed to target the ancestral version of SARS-CoV-2 isolated in Wuhan, China—and they did so quite effectively, showing efficacy against symptomatic disease in the ballpark of 95 percent. But the virus has evolved into variants that can evade vaccine-derived protections. The latest variant, omicron, significantly reduced vaccine effectiveness against symptomatic disease, though protection against severe disease remains strong. Booster doses of the current vaccine design buoy protection but don’t restore the high levels seen previously. And the virus continues to evolve.
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