In a recently published study bioRxiv* In preprint server, researchers tracked immunological evidence for why BQ.1.1 prevalence has increased rapidly in areas where Omicron BA.5 predominates in the United States (US).

Background

Studies have shown that Omicron BQ.1.1 cases have increased rapidly in the US, and Omicron BA.5 cases have dropped to less than half.Not long ago, Omicron BA.5 was the dominant severe respiratory coronavirus-2 (SARS). -CoV-2) variant. Therefore, it is important to determine how BQ.1.1 rescues antibodies (nAbs) induced by the 2019 coronavirus disease (Covid-19) vaccine and SARS-CoV-2 infection.

About the study

In the current study, researchers evaluated 16 individuals vaccinated and boosted with the monovalent mRNA BNT162b2 vaccine in 2021. Next, they evaluated NAB titers in 15 individuals who received monovalent mRNA amplification in 2022. They also evaluated 18 bivalent mRNA boosters. Of the recipients, most received three vaccinations, although some received two or four Covid-19 vaccines.

Research findings

Following addition of monovalent BNT162b2, median nAB 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 mean nAb titers of BQ.1.1 on WA1/2020 and BA.5 were reduced by 175 and 3, respectively.

Compared to the 2021 non-graduation cohort, most of these cohorts may have been infected, although documented rates of SARS-CoV-2 Omicron infections were as low as 33%. Also, WA1/2020 and Omicron nAb titers were higher in the two 2022 groups even before elevation. After growth, their mean NAb titers to 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 escaped nAbs and were effective in early infection and vaccination. The effect was most pronounced for BQ.1.1, whose NATs were seven times lower than BA.5 across study groups.

These findings provide an immunological explanation for the rapid increase in BQ.1.1 prevalence in regions of the US where BA.5 predominates, with implications for both vaccines and natural immunity. Also, the presence of the R346T mutation in several new Omicron subvariants suggests that it may be the result of convergent evolution.

* Important notice

bioRxiv publishes primary scientific reports that are not peer-reviewed and therefore should not be considered as summary, clinical practice/health-related behavior guidance, or as definitive information.