Florian Krammer is a Professor of Microbiology at Mount Sinai's Icahn School of Medicine, one of the world's leading influenza vaccine researchers and the scientist behind the Universal flu vaccine concept targeting the haemagglutinin stalk domain.Source: https://icahn.mssm.edu/profiles/florian-krammer

What is a universal influenza vaccine and how close are we to having one?

A Universal influenza vaccine would target conserved viral proteins like the haemagglutinin stalk, providing protection across multiple subtypes without annual reformulation; Krammer's stalk-based candidates have reached Phase II trials, but broader clinical validation and regulatory approval remain years away.Source: Krammer et al., Nature Reviews Drug Discovery

Does prior flu infection protect against H5N1 bird flu?

Krammer's research shows that antibodies from 2009 pdm09 H1N1 infection or vaccination have partial cross-reactivity to H5N1, likely reducing severe disease risk in a pandemic scenario but not preventing infection outright.Source: Krammer lab publications, Mount Sinai CEIRR

Background

Florian Krammer is Professor of Microbiology at the Icahn School of Medicine at Mount Sinai in New York and co-principal investigator of Mount Sinai's Center for Excellence in Influenza Research and Response (CEIRR). He trained at the University of Vienna and has published over 400 peer-reviewed papers on influenza virus biology, antigen design, serology, and vaccine immunogenicity, making his group one of the most cited in influenza vaccinology.

Krammer's central scientific contribution is the Universal influenza vaccine concept targeting the haemagglutinin stalk domain, a conserved surface region that mutates FAR more slowly than the head domain used in seasonal vaccines. Eliciting stalk-directed antibodies could in principle provide broad subtype protection without annual reformulation. This work has attracted major NIH and BARDA funding and entered Phase II clinical trials. His group's serology assays are used by WHO and CDC for population-level immunity assessments.

On H5N1, Krammer's public focus centres on cross-reactive immunity: serosurvey data indicate that widespread exposure to pdm09 H1N1 since 2009 generates cross-reactive antibodies to group 1 haemagglutinins that correlate with reduced hospitalisation risk, even if they are not sterilising against H5N1. The Science Advances finding that H5N1 binds N-linked sialic acid receptors concentrated in cow udder tissue explains why roughly 1,053 US dairy herds across 17 states were infected for approximately two years before detection, as the virus presented as mastitis rather than respiratory illness. Krammer has argued publicly that the extended undetected circulation represents a substantial spillover opportunity and has advocated for faster H5N1 vaccine candidate stockpiling. A key open question for his research is how cross-reactive antibody titres from pdm09 exposure translate into protection against the specific B3.13 clade circulating in US dairy herds.

More questions

Why is the haemagglutinin stalk a better vaccine target than the head?

The haemagglutinin stalk mutates FAR more slowly than the head domain, meaning stalk-directed antibodies remain effective across different viral strains and seasons, whereas current head-targeted seasonal vaccines require reformulation each year as the virus evolves.Source: Krammer, Cell Host and Microbe, universal flu vaccine review

How worried should we be about H5N1 in dairy cows becoming a pandemic?

Krammer argues the risk is real but partially mitigated by cross-reactive immunity from prior H1N1 exposure; the key unknowns are whether the virus acquires efficient human-to-human transmission mutations and how quickly a matched vaccine could be produced at scale.Source: Krammer public statements, STAT News, 2024-2025

Why did H5N1 go undetected in US dairy herds for so long?

A Science Advances study showed H5N1 binds sialic acid receptors in cow udder tissue, causing mastitis rather than respiratory illness. Surveillance systems designed for respiratory pathogens missed it for roughly two years across more than 1,000 herds.Source: Science Advances (Kuchipudi et al.)

Does prior flu infection protect against H5N1?

Florian Krammer's serology research finds that exposure to pdm09 H1N1 since 2009 generates cross-reactive antibodies to group 1 haemagglutinins, which correlate with reduced hospitalisation risk but are not sterilising against H5N1.Source: Mount Sinai CEIRR

What is a universal flu vaccine and how does it work?

Krammer's Universal vaccine concept targets the conserved haemagglutinin stalk domain, which mutates FAR more slowly than the head domain used in current seasonal vaccines, potentially providing broad cross-subtype protection without annual reformulation.Source: NIH/BARDA-funded clinical trials

How many US dairy herds have H5N1?

By the time the udder-tropism finding was published in Science Advances in June 2026, H5N1 had circulated undetected in roughly 1,053 US dairy herds across 17 states for approximately two years.Source: Science Advances (Kuchipudi et al.)

Source Material

Florian Krammer