As researchers study how well the omicron-targeting boosters work against the now-dominant subvariant XBB.1.5, here's what five recent studies found:
1. The boosters were "barely susceptible" to neutralizing BQ.1 and XBB, according to researchers from New York City-based Columbia University and Ann Arbor-based University of Michigan. Compared to BA.5, omicron subvariant BQ.1.1 was six times more resistant to neutralization, according to the study published Dec. 13 in Cell. XBB.1 — "the most antigenically distinct of the Omicron subvariants" — was 49 times more resistant than BA.5.
2. The bivalent booster offered 73 percent more protection against hospitalization among immunocompetent adults 65 and older, according to the CDC. The results did not indicate variant-specific vaccine effectiveness because the analysis timeline included "both BA.5- and BQ.1/BQ.1.1-predominant periods."
3. When tested among subvariants, omicron sublineages BQ.1.1 and BA.2.75.2 were the most evasive to the bivalent vaccine, according to a study published Dec. 5 in The Lancet.
4. Compared to people 65 and older, younger and middle-aged adults are less protected against hospitalization after receiving the booster, but it still offers moderate protections, CDC data shows.
5. Here are the geometric mean titers with each subvariant, according to a Nov. 4 preprint:
USA-WA1/2020 — 1533
BA.5 — 95
BF.7 — 69
BA.4.6 — 62
BA.2.75.2 — 26
BQ.1.1 — 22
XBB.1 — 15