Covid changes its face. JN.1, the latest dominant variant of the Sars-CoV-2 virus, has been evolving for some time, giving rise to subvariants with additional mutations nicknamed Flirt, capable of spreading more quickly. One in particular is running: it’s called KP.2 and is under the spotlight of experts. In the United States, in fact, this ‘daughter’ of JN.1 has surpassed its ‘mother’. According to the latest data from the Centers for Disease Control and Prevention (CDC), you are now responsible for one in 4 infections (24.9% against 22% from JN.1). “The spread has been rapid” and the rate of KP.2 infections “reached 20% in the UK at the beginning of April”, suggesting that it has the potential to “become predominant globally”. This is explained by the authors of a preliminary study published on the ‘bioRxiv’ pre-print platform, which indicates that KP.2 is “more transmissible and immunoevasive” than JN.1.
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«The rapid emergence and diversification of the JN.1 variant and its KP.2 descendant, which shows significant mutations in the structure of the Spike protein and increased resistance to existing vaccines, highlight the need for further research to understand the implications» of the new variant Flirting «for public health and vaccine development». This is the premise of the scientists coordinated by Kei Sato of the University of Tokyo in Japan, who analyzed 30 genomic sequences of KP.2 from the United States, UK and Canada. Using specific models they then calculated the transmissibility index Re (effective reproduction rate, i.e. the average number of people that an infected person infects) of the new variant, and with virological tests they evaluated its infectivity and immune evasion. The researchers concluded that KP.2 exhibits “significantly improved epidemiological fitness compared to its predecessors, including the XBB lineage. This is confirmed by the estimated Re for KP.2 in the USA, UK and Canada, respectively 1.22, 1.32 and 1.26 times higher than that of JN.1″.
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Despite the greater transmissibility, «the infectivity of KP.2 was significantly lower (10.5 times) compared to that of JN.1», an element which according to the authors could suggest «different mechanisms or routes» through which the new variant spreads and establishes itself in the host. KP.2 finally showed a “significant” immune escape capacity, with “a 3.1-fold reduction in susceptibility to neutralization by sera from individuals vaccinated” with monovalent anti-XBB.1.5 vaccines “without previous infection, and by 1.8 times from sera from people with previous infections.” For the scientists, “this greater resistance could partly explain the higher Re of KP.2, indicating a greater ability to evade immune responses compared to JN.1 and other previous variants.”
