BA.5-Bivalent-Booster Elicits Better Neutralization Than Parental Vaccine But Does Not Produce Robust Neutralization Against BA.2.75.2, BQ.1.1, XBB.1
Source: Vaccine News- BA.5 Bivalent Booster Nov 04, 2022 2 years, 2 weeks, 4 days, 15 hours, 14 minutes ago
Vaccine News: A new study by researchers from the Sealy Institute for Vaccine Sciences at the University of Texas Medical Branch Galveston - USA and also from the Department of Biochemistry and Molecular Biology along with the Department of Pathology at the University of Texas Medical Branch, Galveston – USA have found that the new BA.5-Bivalent-Booster elicits better neutralization than parental vaccine but does not produce robust neutralization against the new SARS-CoV-2 BA.2.75.2, BQ.1.1 and XBB.1 variants!
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The study showed low neutralization of SARS-CoV-2 Omicron BA.2.75.2, BQ.1.1, and XBB.1 by 4 doses of parental mRNA vaccine or a BA.5-bivalent booster.
According to various
Vaccine News sources, this is the first study to date to assess the efficacy of 4 doses of parental mRNA vaccine or a BA.5-bivalent booster against the new SARS-CoV-2 Omicron sub-lineages BA.2.75.2 and BQ.1.1, and also the new recombinant sub-lineage XBB.1
Scientist are already aware that the newly emerged SARS-CoV-2 Omicron BQ.1.1, XBB.1, and other sub-lineages have accumulated additional spike mutations that may affect vaccine effectiveness although many health authorities around the world are still advocating these new boosters and extolling their merits despite lack of any proper published research data.
The study team reported the neutralizing activities of three human serum panels collected from individuals 1-3 months after dose 4 of parental mRNA vaccine (post-dose-4), 1 month after a BA.5-bivalent-booster (BA.5-bivalent-booster), or 1 month after a BA.5-bivalent-booster with previous SARS-CoV-2 infection (BA.5-bivalent-booster-infection).
The study findings showed that post-dose-4 sera neutralized USA-WA1/2020, BA.5, BF.7, BA.4.6, BA.2.75.2, BQ.1.1, and XBB.1 SARS-CoV-2 with geometric mean titers (GMTs) of 1533, 95, 69, 62, 26, 22, and 15, respectively; BA.5-bivalent-booster sera improved the GMTs to 3620, 298, 305, 183, 98, 73, and 35; BA.5-bivalent-booster-infection sera further increased the GMTs to 5776, 1558,1223, 744, 367, 267, and 103.
Hence the study findings showed that although BA.5-bivalent-booster elicits better neutralization than parental vaccine, it does not produce robust neutralization against the newly emerged Omicron BA.2.75.2, BQ.1.1, and XBB.1.
Also, previous infection enhances the magnitude and breadth of BA.5-bivalent-booster-elicited neutralization.
The study findings were published on a preprint server and are currently being peer reviewed.
https://www.biorxiv.org/content/10.1101/2022.10.31.514580v1
The study findings support three conclusions:
-Firstly, the BA.5-bivalent booster elicits better neutralization against the newly emerged Omicron sub-lineages than the parental mRNA vaccine.
-Secondly, individuals with SARS-CoV-2 infection history develop higher and broader neutralization against the ongoing Omicron sub-lineages after the BA.5-bivalentbooster.
-Thirdly, among tested Omicron sub-lineages, BA.2.75.2, BQ.1.1, and XB
B.1 exhibit the greatest evasion against vaccine-elicited neutralization, suggesting the potential of these new sub-lineages to dethrone BA.5 as the dominant lineage in circulation.
The researchers however noted that the study has two limitations:
-The study team did not examine the antiviral roles of non-neutralizing antibodies and cell-mediated immunity. These two immune components, together with neutralizing antibodies, protect patients from severe disease and death.
https://pubmed.ncbi.nlm.nih.gov/35289637/
https://pubmed.ncbi.nlm.nih.gov/34237248/
It has also been found that unlike neutralizing antibodies, many T cell epitopes after vaccination or natural infection are preserved in Omicron spikes.
https://pubmed.ncbi.nlm.nih.gov/34909772/
Nevertheless, robust antibody neutralization is critical to prevent viral infection.
https://pubmed.ncbi.nlm.nih.gov/36044620/
The next limitation was that the study team did not define the spike mutations that contribute to the observed immune evasion of the newly emerged Omicron sub-lineages.
The Spike mutation F486V was previously shown to drive the immune evasion of BA.4/5.
https://pubmed.ncbi.nlm.nih.gov/35792746/
The new Omicron sub-lineages BA.2.75.2, BA.4.6, BF.7, BQ.1.1, and XBB.1 share the spike R346T mutation that was reported to confer higher neutralization evasion.
https://pubmed.ncbi.nlm.nih.gov/36179744/
However, despite these limitations, the study findings along with real world effectiveness of BA.5-bivalent-booster, will hopefully guide vaccine strategy against the current and future Omicron sub-lineages.
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