IntroductionDespite extensive research on COVID-19 vaccines, comparative data on the long-term humoral response across multiple vaccine platforms and heterol...

SARS-CoV-2 has emerged as the 5th endemic coronavirus and immunological cross protection between coronaviruses will influence their infectivity and clinical impact. We determined adaptive immunity against the spike protein of each human coronavirus during the course of the COVID-19 pandemic. A characteristic pattern of HCoV immunodominance, dominated by OC43 and 229E, was apparent prior to SARS-CoV-2 and was largely unaffected by SARS-CoV-2 infection, which itself elicited moderate antibody titre. Vaccination or hybrid immunity elicited supraphysiological levels of coronavirus-specific antibodies, only a proportion of which was cross-reactive with SARS-CoV-2 spike indicating substantial backboosting of HCoV-specific responses. SARS-CoV-2 vaccination focused antibody responses against the S1 domain of SARS-CoV-2 spike whilst T cell responses recognised peptides equivalently across S1 and S2. Coronavirus-specific T cells exhibited strong production of IFN-γ, IL-2 and CXCL8. In summary, the entry of SARS-CoV-2 into its ecological niche has impacted marginally on relative immunity against other human coronaviruses although vaccination provides a modest antibody increment which is unlikely to be maintained. Further, although SARS-CoV-2 vaccination elicits spike-specific adaptive immune responses that are focused against the S1 domain, thereby favouring neutralising antibodies, the natural history of HCoV immunity indicates that adaptive responses may transition towards S2 recognition across the life course. A prospective analysis reveals that emergence of SARS-CoV-2 has had only a marginal impact on the immune response to spike protein of other endemic human coronaviruses and predicts limited cross protection against infection.

Objective To estimate associations between trivalent influenza vaccination and COVID-19 mortality as well as severe clinical outcomes among hospitalised patients. Design Retrospective observational study. Setting This study was conducted among hospitalised patients with COVID-19 in Brazil. Participants We analysed all hospitalised patients with COVID-19 with available vaccination information captured in Brazil’s national electronic respiratory infection data system between 1 January 2020 and 23 June 2020. Main outcome measures The primary outcomes were age-specific mortality rates of hospitalised patients with COVID-19 with and without recent inactivated trivalent influenza vaccination. Results A total of 53 752 clinically confirmed COVID-19 cases were analysed. Controlling for health facility of treatment, comorbidities as well as an extensive range of sociodemographic factors, patients who received a recent influenza vaccine experienced on average 7% lower odds of needing intensive care treatment (95% CI 0.87 to 0.98), 17% lower odds of requiring invasive respiratory support (95% CI 0.77 to 0.88) and 16% lower odds of death (95% CI 0.78 to 0.90). Protective effects were larger when the vaccine was administered after onset of symptoms as well as among younger patients. Conclusion Patients with COVID-19 with recent inactivated influenza vaccination experience significantly better health outcomes than non-vaccinated patients in Brazil. Beneficial off-target effects of influenza vaccination through trained innate immune responses seem plausible and need to be further explored. Large-scale promotion of influenza vaccines seems advisable, especially in populations at high risk for severe COVID-19 disease progression. Data are publicly available at the Brazilian Ministry of Health website.

Nature - Two distinct patterns in the protective effect of natural infection against reinfection in the Omicron variant versus pre-Omicron eras show that SARS-CoV-2 immune protection is shaped by...

For the past 15 years, the fact-checkers at PolitiFact have sorted through hundreds of statements by politicians to name the "Lie of the Year." This year, the editors dubbed 2025 the "Year of the Lies." Lisa Desjardins discussed more with PolitiFact Editor-in-Chief Katie Sanders. A warning: some images in this story are disturbing.

Since 2021, highly pathogenic avian influenza viruses (HPAIV) belonging to H5N1 clade 2.3.4.4b have caused high mortality in North American wild birds and poultry. In 2025, a new D1.1 genotype caused two human deaths and host-switched to dairy cattle. However, the evolutionary origins and dynamics of D1.1 have not been fully characterized. Here, our phylogenetic analysis of 17,516 H5N1 genome sequences uncovers how D1.1 introduced a major shift in the antigenic diversity and ecology of the H5N1 epizootic in North America. D1.1 is the first major H5N1 genotype to (a) emerge in the Pacific flyway and spread west-to-east faster than any prior genotype; (b) antigenically shift via reassortment with the North American N1 segment, displacing the previously fixed Eurasian N1; and (c) transmit to a broader range of host species than any H5N1 genotype to date, introducing mammalian adaptations. ### Competing Interest Statement The authors have declared no competing interest. Research Foundation - Flanders, https://ror.org/03qtxy027, G098321N, G0E1420N European Union Horizon 2023 RIA project LEAPS, 101094685 DURABLE EU4Health project 02/2023-01/2027, 101102733 Fonds National de la Recherche Scientifique, F.4515.22 European Union Horizon 2020 project MOOD, 874850

The Iranian rial hit a record low against the US dollar on Sunday, prompting shopkeepers in Tehran to stage protests, which have quickly spread.

Since 2021, highly pathogenic avian influenza viruses (HPAIV) belonging to H5N1 clade 2.3.4.4b have caused high mortality in North American wild birds and poultry. In 2025, a new D1.1 genotype caused two human deaths and host-switched to dairy cattle. However, the evolutionary origins and dynamics of D1.1 have not been fully characterized. Here, our phylogenetic analysis of 17,516 H5N1 genome sequences uncovers how D1.1 introduced a major shift in the antigenic diversity and ecology of the H5N1 epizootic in North America. D1.1 is the first major H5N1 genotype to (a) emerge in the Pacific flyway and spread west-to-east faster than any prior genotype; (b) antigenically shift via reassortment with the North American N1 segment, displacing the previously fixed Eurasian N1; and (c) transmit to a broader range of host species than any H5N1 genotype to date, introducing mammalian adaptations. ### Competing Interest Statement The authors have declared no competing interest. Research Foundation - Flanders, https://ror.org/03qtxy027, G098321N, G0E1420N European Union Horizon 2023 RIA project LEAPS, 101094685 DURABLE EU4Health project 02/2023-01/2027, 101102733 Fonds National de la Recherche Scientifique, F.4515.22 European Union Horizon 2020 project MOOD, 874850

npj Vaccines - Systematic analysis of COVID-19 mRNA vaccines using four orthogonal approaches demonstrates no excessive DNA impurities

There was more good health news about the COVID-19 vaccine for infants, kids and adults in December. There’s still time to get the shot this winter.