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#KP2 - based monovalent #mRNA #vaccines robustly boost #antibody responses to #SARS-CoV-2

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By G.M.

{Excerpt}

In response to the ongoing evolution of SARS-CoV-2, vaccine manufacturers have released updated COVID-19 vaccines annually since 2022. For much of 2024, the global spread was dominated by the JN.1 lineage of viruses,1 which are antigenically quite distant from the XBB.1.5 variant that was used in the previous vaccine booster.2 In August 2024, the US Food and Drug Administration authorised two updated mRNA vaccines (Pfizer–BioNTech and Moderna) based on the spike sequence of KP.2, a subvariant in the JN.1 lineage.3 In the UK and the EU, a KP.2-based mRNA vaccine (BioNTech) was also authorised later in the year.4,5 We have now provided the first indication of the acute boosting effect of updated KP.2 monovalent mRNA vaccines (KP.2 MV) on serum SARS-CoV-2 neutralising antibodies in humans. Since the authorisation of the updated vaccine boosters, SARS-CoV-2 has evolved beyond KP.2, with the subvariant KP.3.1.1 becoming dominant globally and the subvariant XEC now gaining traction rapidly.1 KP.2 contains Arg346Thr, Phe456Leu, and Val1104Leu mutations in spike, in addition to those present in the parental JN.1 (figure A). Both KP.3.1.1 and XEC share Phe456Leu and Val1104Leu mutations found in KP.2, along with Gln493Glu, which is absent in KP.2. In addition, KP.3.1.1 harbors the Ser31del mutation, whereas XEC carries Thr22Asn and Phe59Ser mutations; neither KP.3.1.1 nor XEC possess the Arg346Thr mutation (figure A). The effectiveness of the updated KP.2 MV boosters on neutralising antibodies in human serum against recently dominant subvariants has yet to be reported.

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Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00058-1/fulltext?rss=yes

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