Q: Will this fall’s updated COVID-19 vaccines be effective against EG.5?
A: Yes, the updated COVID-19 vaccines that will become available in the U.S. this fall are predicted to retain effectiveness against subvariant EG.5, which has risen in prevalence both nationally and globally during summer 2023. EG.5 is a descendent of XBB.1.9.2 and shares very similar spike proteins to other XBB sublineages; it is sometimes colloquially referred to as “Eris,” though this label is not recognized by CDC or WHO.
mRNA vaccine manufacturers are reformulating fall 2023 vaccines to target the XBB lineage, following a unanimous recommendation by FDA’s Vaccines and Related Biological Products Advisory Committee and conforming with advice from WHO.
The specific strain of this fall’s updated vaccines will be targeted against XBB.1.5, which shares a nearly identical spike amino acid profile with EG.5. Therefore, updated vaccines are likely to offer added protection, especially against severe disease, for people at higher risk of severe COVID-19 outcomes. EG.5 does carry an additional F456L amino acid mutation in its spike protein, and its subvariant EG.5.1 carries additional spike mutation Q52H (WHO, August 2023 [PDF]), which may affect neutralizing antibody levels and contribute to breakthrough infections.
HHS is expected to announce an updated U.S. vaccine availability timeline and recommendations within the next month.