SARS-CoV-2 Omicron’s Latest Subvariant BQ.1.1 Shows Remarkable Immune Evasion Potential Against Vaccine Sera

In a recent study published on bioRxiv* preprint server, the researchers searched for immunological evidence why the prevalence of BQ.1.1 increased rapidly in areas where Omicron BA.5 was dominant in the United States (US).

study: Avoidance of significant neutralization by SARS-CoV-2 Omicron variant BQ.1.1. Image Credit: Naeblys/Shutterstock

Background

Studies have shown that Omicron BQ.1.1 cases have increased rapidly in the US, and Omicron BA.5 cases have decreased to less than half, where not long ago, Omicron BA.5 was the predominant severe acute respiratory syndrome coronavirus -2 (SARS). -CoV-2) variant. Therefore, it is crucial to determine how BQ.1.1 avoids neutralizing antibodies (nAbs) induced by vaccination against corona virus 2019 (COVID-19) and SARS-CoV-2 infection.

About the study

In this study, researchers assessed nAb titers in 16 individuals who were vaccinated and boosted with the monovalent mRNA BNT162b2 vaccine in 2021. They then assessed nAb titers in 15 individuals who received the monovalent mRNA booster in 2022. In addition, bivalent, mRNA booster recipients, most of whom received three doses of the vaccine, although some received two or four doses of the COVID-19 vaccine.

Study findings

After monovalent BNT162b2 boost, median nAb titers to WA1/2020, BA.5, BF.7, BA.2.75.2, and BQ.1.1 were 45, 695, 887, 595, 387, and 261, respectively. The authors noted that the median nAb titers against BQ.1.1 were much reduced than the median nAb titers against WA1/2020 and BA.5 by factors of 175 and 3, respectively.

Compared to the uninfected 2021 cohort, the majority were likely infected in these cohorts, although the documented SARS-CoV-2 Omicron infection rate was as high as 33%. Also, WA1/2020 and Omicron nAb titers were higher in the two 2022 cohorts even before boosting. After boosting, their mean NAb titers on WA1/2020, BA.5, BF.7, BA.2.75.2, and BQ.1.1 were 40,515, 3693, 2399, 883, and 508, respectively.

Conclusions

The results of the study showed that compared to BA.5, both BA.2.75.2 and BQ.1.1 more efficiently escaped nAbs elicited by prior infection and vaccination. The effect was most pronounced for BQ.1.1, whose nAb titers were lower than BA.5 by a factor of seven in all studied cohorts.

These findings provide an immunological explanation for the rapid increase in BQ.1.1 prevalence in regions where BA.5 was dominant in the US, with implications for both vaccine and natural immunity. Also, it puts into perspective how the presence of the R346T mutation in multiple new Omicron subvariants is likely due to convergent evolution.

*Important notice

bioRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered definitive, guiding clinical practice/health behavior or treated as established information.