Influenza A(H3N2) subclade K (J.2.4.1) has dominated the 2025/26 season start in England. Post-infection ferret antisera raised against northern hemisphere 2025/26 vaccine strains showed reduced reactivity to subclade K viruses in England, aligning with World Health Organization reports. Nevertheless, early post-vaccination, vaccine effectiveness against influenza-related emergency department attendances and hospital admissions remained within typical ranges, at 72–75% in children and adolescents (< 18 years) and 32–39% in adults. Hence, vaccination remains effective against clinical disease caused by influenza A(H3N2) viruses.

Job title: Postdoctoral Research Fellowship in Chromatin Biology and Cancer Epigenetics (283381), Employer: University of Oslo, Deadline: Wednesday, August 20, 2025

Ingen er tjent med en overdramatisering og spekulativ fremstilling av hvordan pandemien kan ha blitt til.

New immune evasive variants of SARS-CoV-2 may increase infections and hospitalizations in risk groups, such as the elderly. In this study, we evaluated neutralizing antibodies against KP.3.1.1 and XE....

Job title: Researcher in Computational Biology and Cancer Epigenetics&nbsp; (275425), Employer: University of Oslo, Deadline: Monday, March 31, 2025

The repeated spill-over of Influenza A virus H5N1 clade 2.3.4.4b from cattle to humans highlights the risk of a human H5N1 pandemic. Given the impact of pre-existing immunity on the course and severity of viral infections, we assessed in detail the humoral immunity against the H5N1 A/Texas/37/2024 isolate in H5N1-naïve individuals. To this end, we performed complementary binding and neutralization assays on 66 subjects and ranked activities among a panel of 76 influenza A virus isolates. We detected low but distinct cross-neutralizing titers against A/Texas/37/2024 with a 3.9 to 15.6-fold reduction compared to selected H1N1 or H3N2 strains. Moreover, by cloning and evaluating 136 monoclonal antibodies from single memory B cells, we identified potent A/Texas/37/2024-neutralizing monoclonal antibodies in five out of six investigated individuals. These antibodies predominantly utilize VH1-69 gene segments, cross-neutralize H1, and compete with antibodies targeting the HA stem. Our findings demonstrate partial pre-existing humoral immunity to A/Texas/37/2024 in H5N1-naïve individuals. ### Competing Interest Statement DR, MM, CK, FK, and ML are members of the non-profit Center for Predictive Analysis of Viral Evolution (Previr). LG, HG, CK and FK are inventors on patent applications on virus neutralizing antibodies filed by the University of Cologne and have received payments from the University of Cologne for licensed patents.

En vaksineskeptiker kan bli helseminister. Nobelpris-vinnere slår alarm, skriver Per Helge Måseide.

Eldre har lavt nivå av beskyttende antistoffer mot de nyeste varianter av SARS-CoV-2 viruset viser en ny studie fra Folkehelseinstituttet. Derfor bør eldre ta oppfriskningsdose med koronavaksine.

As of November 2024, SARS-CoV-2 Omicron JN.1 subvariants, such as KP.2 (JN.1.11.1.2), KP.3 (JN.1.11.1.3), KP.3.1.1 (JN.1.11.1.3.1.1), and XEC, a recombinant lineage between KS.1.1 (JN.13.1.1.1) and KP.3.3 (JN.1.11.1.3.3), have been circulating in several countries. To control the infection with SARS-CoV-2 Omicron JN.1 subvariants, JN.1 monovalent mRNA vaccines have been developed. Some previous reports showed that the JN.1 monovalent mRNA vaccine of Pfizer/BioNTech (US/Germany) increased antiviral humoral immunity against JN.1 subvariants and XEC. However, the efficacy of other available JN.1 monovalent mRNA vaccines (e.g., Daiichi-Sankyo, Japan) remains unassessed. To validate the antiviral efficacy induced by JN.1 mRNA vaccines, sera were collected from individuals vaccinated with Pfizer/BioNTech JN.1 mRNA vaccine (N=15) or Daiichi-Sankyo JN.1 mRNA vaccine (N=19) before and 3-4 weeks after vaccination. We then performed a neutralization assay using these sera and pseudoviruses. Both Pfizer/BioNTech JN.1 vaccine (2.4- to 8.0-fold, P=0.0001) and Daiichi-Sankyo JN.1 vaccine (2.3- to 13-fold, P=0.0001) boosted antiviral humoral immunity against all variants tested with statistical significance. While the Pfizer/BioNTech mRNA vaccine encodes the full-length JN.1 spike (S), the Daiichi-Sankyo mRNA vaccine encodes the receptor-binding domain of JN.1 S. Our data suggest that the receptor-binding domain of JN.1 S can effectively induce antiviral humoral immunity against JN.1 subvariants and XEC comparable to the full-length JN.1 S. However, it should be considered that the sizes of our cohorts are relatively small (<20 donors per cohort), and donor characteristics, such as age, sex, underlying disease status, and previous SARS-CoV-2 infection, may critically affect the experimental results. Future investigations with larger cohorts will address this concern. When compared to vaccination with JN.1 mRNA vaccines, our previous investigations showed that the natural infection of JN.1 and KP.3.3 elicited poorer antiviral humoral immunity against JN.1 and its subvariants. Our results suggest that the JN.1 mRNA vaccination more robustly induces antiviral humoral immunity against recent JN.1 subvariants than the natural infection of JN.1 subvariants regardless of manufacturer. Moreover, as we reported last year, the humoral immunity induced by XBB.1.5 monovalent mRNA vaccine against XBB.1.5 was weaker than that against ancestral B.1.1. However, in the case of JN.1 monovalent mRNA vaccine, here we showed that the 50% neutralization titer against XBB.1.5 is greater than that against ancestral B.1.1. These observations imply that immune imprinting has shifted from that biased toward pre-Omicron to that biased toward Omicron, depending on the time and/or number of immune stimuli (e.g., infection and/or vaccination). ### Competing Interest Statement K.S. has consulting fees from Moderna Japan Co., Ltd. and Takeda Pharmaceutical Co. Ltd. and honoraria for lectures from Gilead Sciences, Inc., Moderna Japan Co., Ltd., and Shionogi & Co., Ltd. The other authors declare no competing interests. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

New immune evasive variants of SARS-CoV-2 may increase infections and hospitalizations in risk groups, such as the elderly. We evaluated neutralizing antibodies against recent variants KP.3.1.1 and XEC, that are either widely distributed or on the rise globally, in sera from a cohort of seniors aged 65+ years from May 2024. Neutralizing responses were low against both KP.3.1.1 and XEC in the seniors, suggesting that further efforts to increase vaccine uptake in seniors are warranted. ### Competing Interest Statement The authors have declared no competing interest.