Credit ACIP/CDC
#17,099
A week ago, in Preprint: Immunogenicity of the BA.5 Bivalent mRNA Vaccine Boosters, we looked at two preprints that suggested the new bivalent mRNA booster shots for COVID might not provide any more protection against the newer Omicron variants than the original booster.
Both papers cited immune imprinting from prior antigenic exposure as potential obstacles in creating newer boosters.
While this wasn't the home run that the vaccine manufacturers (and the government) were hoping for, I cautioned that these were small, preliminary, laboratory studies and they may not be telling us the full story.
As we've seen often in the past (see Why Preprints Are Only Preprints), reputable researchers can look at the same problem - and because they employ different methods - arrive at different conclusions.Which is why it is important to look at the preponderance of evidence, not just a single study.
Which brings us to a new preprint, published yesterday by researchers from Emory, Stanford, and NIAID, that suggests the new bivalent boosters may perform better against up-and-coming Omicron subvariants BA.2.75.2 and BQ.1.1.
Why the difference?
One possibility: the original analyses used a constructed pseudovirus (which are safer to work with, since they don't replicate), while this latest study used a live virus for use in their neutralization assays.
This may not be the only difference, but it stands out.
In any event, this latest paper found the performance of the booster shot significantly improved over the older booster when tested against several Omicron subvariants, including BA.5, BA.2.75.2 and BQ.1.1.
This obviously won't be the final word on the topic, as real-world data on breakthrough infections will trump all lab findings. But it is encouraging.
I've reproduced the abstract below. Follow the link to read the full preprint. I'll have a brief postscript after the break.
mRNA bivalent booster enhances neutralization against BA.2.75.2 and BQ.1.1
Meredith E Davis-Gardner, Lilin Lai, Bushra Wali, Hady Samaha, Daniel Solis, Matthew Lee, Andrea Porter-Morrison, Ian Thomas Hentenaar, Fumiko Yamamoto, Sucheta Godbole, Daniel C Douek, Frances Eun-Hyung Lee, Nadine Rouphael, Alberto Moreno, Benjamin A Pinsky, Mehul S Suthardoi: https://doi.org/10.1101/2022.10.31.514636
Abstract
The emergence of the highly divergent SARS-CoV-2 Omicron variant has jeopardized the efficacy of vaccines based on the ancestral spike. The bivalent COVID-19 mRNA booster vaccine within the United States is comprised of the ancestral and the Omicron BA.5 spike. Since its approval and distribution, additional Omicron subvariants have been identified with key mutations within the spike protein receptor binding domain that are predicted to escape vaccine sera.
Of particular concern is the R346T mutation which has arisen in multiple subvariants, including BA.2.75.2 and BQ.1.1.
Using a live virus neutralization assay, we evaluated serum samples from individuals who had received either one or two monovalent boosters or the bivalent booster to determine neutralizing activity against wild-type (WA1/2020) virus and Omicron subvariants BA.1, BA.5, BA.2.75.2, and BQ.1.1.
In the one monovalent booster cohort, relative to WA1/2020, we observed a reduction in neutralization titers of 9-15-fold against BA.1 and BA.5 and 28-39-fold against BA.2.75.2 and BQ.1.1. In the BA.5-containing bivalent booster cohort, the neutralizing activity improved against all the Omicron subvariants.
Relative to WA1/2020, we observed a reduction in neutralization titers of 3.7- and 4-fold against BA.1 and BA.5, respectively, and 11.5- and 21-fold against BA.2.75.2 and BQ.1.1, respectively. These data suggest that the bivalent mRNA booster vaccine broadens humoral immunity against the Omicron subvariants.
While this study suggests the bivalent booster is more effective against these Omicron subvariants than the older booster, these viruses still have a much higher immune escape ability than their ancestors, and breakthrough infections - even among the booster - are to be expected.
But the booster may just be the difference between getting mildly ill, or hospitalized. Or between making a full recovery, and enduring `Long COVID'.
While a good outcome isn't guaranteed, getting booster almost certainly improves your chances.
