SARS-CoV-2 Update
by Prof. Hervé Fleury, MD-PhD | Ventum Biotech Scientific Board Member
The situation in the USA is often a reflection of what happens a few weeks or months later in Western Europe. As such, it deserves to be studied, especially since the US data are of high scientific, virological and epidemiological quality.
Figure 1
Figure 2
In the first figure, we see the KP.3 variant taking over the other variants in the USA. In the second figure (Kaku et al. Lancet Infectious Diseases, June 2024), we find the KP.3 variant in the Omicron lineage that we have known for several years; in this lineage, we experienced the BA.2.86 variant in July 2023 and then the JN.1 variant, which has a mutation at position 455 of the spike protein compared to 2.86; the KP.2 and KP.3 variants derive from JN.1 with the 455 mutation as well as the 456.
The mutations observed in successive variants of Sars Cov 2 have given it greater infectivity but also less pathogenicity compared to the initial Wuhan strain of 2019. Overall, these variants remained susceptible to vaccine antibodies, albeit at a lower level.
Pfizer and Moderna have been offering since September 2023 an mRNA vaccine based on the Omicron XBB1.5 strain; this vaccine has greater efficacy against the latest variants to appear in the Omicron lineage, including BA.2.86; its effectiveness on JN.1 is lower; the Japanese team (Kaku et al.) has just evaluated the action of the antibodies generated by the XBB1.5 vaccine against KP.2 and KP.3; they have very low efficacy; however, subjects who have had a natural infection and have been vaccinated with XBB1.5 have a higher antibody titer against KP.2/KP.3. However, these comments must be balanced by specifying that although the titer of antibodies generated against JN.1 and KP by the XBB1.5 vaccine is low, vaccination still protects against major complications that can lead to serious hospitalization.
Let's not forget that a natural or vaccine antiviral defense combines the synthesis of circulating antibodies with cellular immunity linked to TCD8+ lymphocytes, the latter of which can be maintained between the different variants.
The idea now is to generate a vaccine against JN.1 that should have an effective action on KP variants. KP.3 has already arrived in Europe and France; It should logically impose itself more strongly at the time of the Olympic Games because of the mixing of populations in the Paris region.
While waiting for a monovalent JN.1 vaccine (some US companies such as Novavax are on the way), a booster of the XBB1.5 vaccine will be recommended in the fall of 2024 at the same time as the flu vaccination, especially in elderly subjects as well as in diabetics and patients on immunosuppressants.
Finally, it should be noted that the antiviral drug Paxlovid remains effective against all variants.
