The FDA’s Vaccines and Related Biological Products Advisory Committee has voted to recommend updating this fall’s Covid-19 vaccines to target the XFG variant, a fast-spreading omicron hybrid strain nicknamed “stratus.”
XFG carries mutations that could help it partially dodge Covid antibodies, Natalie Thornburg, PhD, who leads the CDC’s respiratory division, told the panel at a May 28 meeting. XFG.1.1 — currently the most prevalent lineage in the U.S. — carries 12 spike protein substitutions compared to LP.8.1, the strain targeted by this season’s shots. The committee’s recommendation is designed to give manufacturers time to reformulate ahead of the fall and winter surge season.
Most circulating viruses remain JN.1 descendants, with XFG and NB.1.8.1 among the most prevalent lineages, according to CDC genomic surveillance data. A minority of detected cases involve BA.3.2, a phylogenetically distinct variant, first identified in South Africa in November 2024, that continues to diversify but remains a small share of U.S. infections.
CDC data show cumulative Covid-19 hospitalization rates during the 2025–2026 season are running lower than prior seasons, though risk remains highest among infants under 6 months and adults 65 and older — groups whose hospitalization rates are comparable to influenza.
The committee’s recommendation is not final. The FDA is expected to give vaccine makers the go-ahead to begin production, though the agency has neither a permanent vaccine chief nor a commissioner. It has also faced recent scrutiny after blocking publication of multiple vaccine safety studies earlier this month, despite findings that serious side effects were rare.
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