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28th January 2021
The Moderna vaccine, mRNA-1273, has been shown to elicit high levels of neutralising antibody titres in clinical trials. However, with the identification of COVID-19 variants, a major concern is whether the range of vaccines available are capable of generating sufficient immunity. The UK COVID-19 variant, termed B.1.1.7, has 17 mutations, 8 of which are in the spike protein and two of which, 69-70 del and N501Y, have led to a particular concern that the variant is much more easily transmitted and potentially associated with a higher mortality. The other variant identified, B.1.351, has emerged from South Africa and as with the UK variant, evidence suggests that B.1.351 is more transmissible and produces a higher viral load among those who become infected. In fact, genomic analysis shows that mutations in the S protein are more extensive in B.1.351, with 3 of these present in the receptor binding domain, which is the target for neutralising antibodies which could affect vaccine efficacy. For this recent, but unpublished, study, researchers from Moderna, the vaccine manufacturer, sought to assess the neutralisation of sera from eight patients (aged 18 to 55) who had already received two doses of the company’s vaccine. In an effort to test the effectiveness of m-RNA-1273, the researchers created and tested pseudo viruses, that contained either a partial or a complete set of mutations present in the B.1.1.7 and B.1.351 lineages.
With respect to the B.1.1.7 lineage, both the partial and complete pseudo viruses, containing the recognised mutations, had minimal effect on the production of neutralising antibodies, i.e., the vaccine was just as effective against this variant as the original COVID-19 strain. In contrast, there was a significant decrease in neutralising titres measured against either the partial or complete mutations found within the B.1.351 variant. In fact, antibody titres were approximately 6-fold lower relative to other variants for the complete set of mutations. Nevertheless, the authors reported that the antibody titres generated against the complete B.1.351 pseudo virus, while lower than for B.1.1.7, were still generally high enough to provide protection if vaccinated with the mRNA-1273.
Wu K et al. mRNA-1273 induces neutralising antibodies against spike mutants from global SARS-CoV-2 variants. 2021 https://doi.org/10.1101/2021.01.25.427948https://doi.org/10.1101/2021.01.25.427948