Researchers from the USA have conducted a study showing that Moderna’s mRNA-1273 vaccine neutralizes all circulating variants of SARS-CoV-2 tested to date. Concerns have been raised with the increasing transmission rates and higher viral loads associated with the recently emerged B.1.1.7 (UK) and B.1.351 (South Africa) variants. There were also concerns that these strains may potentially circumvent immunity conferred by natural infection or vaccination. The researchers assessed the neutralization capacity of sera from eight Phase 1 clinical trial participants and from non-human primates (NHPs) that had received the mRNA-1273 vaccine.
Neutralization was measured against the original SARS-CoV-2 isolate from Wuhan, China; the D614G variant that then became dominant; the B.1.1.7 and B.1.351 variants, and other variants that have previously emerged (20E, 20A.EU2, D614G-N439K, and mink cluster 5 variant). All samples from both the clinical trial participants and NHPs fully neutralized all of the SARS-CoV-2 strains tested. No significant impact on neutralization capacity against the B.1.1.7 variant was observed whether antibody titers were measured against the full set of mutations or the 69-70 deletion only.
Of all the variants tested, the only one that reduced levels of neutralizing antibodies was B.1.351. Sera from the clinical trial participants showed a 2.7-fold reduction in neutralization when the three mutations (K417N, E484K, N501Y) found in the spike RBD were included. However, neutralizing titers remained above the levels previously found to confer protection in NHPs and all samples from both the clinical trial participants and NHPs fully neutralized the B.1.351 variant. Viral escape was not detected in any of the samples tested.
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