Moderna’s updated COVID-19 shot shows ‘significant boost’ in antibodies against ‘Eris’ strain

Moderna’s updated COVID-19 shot, set to be deployed this fall, induced a “significant boost” of antibodies of the EG.5 omicron subvariant, nicknamed the Eris strain, according to preliminary clinical trial data from the company.

When Moderna filed for authorization from the Food and Drug Administration (FDA) for its updated shot earlier this year, it cited how its vaccine contained spike proteins for the XBB.1.5 omicron subvariant, which was the dominant strain in the U.S. at the time of filing.

The Eris subvariant has since grown to command a small majority of cases in the U.S., accounting for 17.3 percent of cases. Similarly descending from the XBB omicron subvariant, it is closely related to XBB.1.5, and cross-protection is likely to occur.

Moderna said in a statement Monday that “preliminary clinical trial data confirm its updated COVID-19 vaccine for the fall 2023 vaccination season showed a significant boost in neutralizing antibodies against EG.5 and FL.1.5.1 variants.”

“These results suggest that Moderna’s updated COVID-19 vaccine may effectively target the expected circulating variants of COVID-19 during the upcoming vaccination season,” the company said.

Only three of the 10 regions monitored by the Department of Health and Human Services (HHS) are reporting genomic data on COVID-19, making the full picture of variant dominance in the U.S. unclear.

In the Northeast region, the FL.1.5.1 omicron subvariant, also descended from the XBB subvariant, exceeds Eris and accounts for one-fifth of estimated cases.

In June, an FDA panel unanimously voted to recommend that the next round of vaccination in the U.S. should only have protection against XBB variants, citing their worldwide dominance and following the World Health Organization’s (WHO) guidance.

While Moderna’s updated shot was indicated against XBB.1.5 when it filed for authorization, stakeholders acknowledged that variant dominance was subject to change, anticipating that whichever strain was most prevalent at the time of the vaccine campaign would be closely related enough for the vaccines to still be effective.

The WHO initially designated Eris as a “variant under monitoring,” indicating it had potential growth advantages but more information was needed. The WHO altered Eris’s designation to a “variant of interest” earlier this month, indicating it had genetic changes affecting its viral capabilities, though the organization did not find cause for alarm yet.

The WHO also noted that the strain from which Eris descends from has the “same spike amino acid profile as XBB.1.5,” which is what mRNA vaccines like Moderna’s target.

“Based on the available evidence, the public health risk posed by EG.5 is evaluated as low at the global level, aligning with the risk associated with XBB.1.16 and the other currently circulating VOIs,” the WHO said in a risk evaluation published earlier this month. “While EG.5 has shown increased prevalence, growth advantage, and immune escape properties, there have been no reported changes in disease severity to date.”