Dear colleagues and friends,

On behalf of the European Society for Immunodeficiencies (ESID), the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) with its Immunocompromised Host Working Group, and the European Society for Paediatric Infectious Diseases (ESPID), it is our great pleasure to invite you to a joint focus meeting in Vienna, Austria, in late November 2027.

Infectious diseases have always been among the most relevant topics in the field of inborn errors of immunity (IEI), including primary and secondary immune disorders (PID and SID). Increased susceptibility to infections, atypically severe courses of specific infections and infection-associated malignancies are a fascinating area of biological research and, at the same time, a demanding clinical interface.

Just as autoimmunity, autoinflammation, allergy and tumour predisposition are now firmly recognised as integral parts of IEI beyond infections, the interplay between immunology and infection deserves a dedicated platform of its own.

For ESID, our last joint focus meeting, The Interplay of Hematology & Immunology (ESID, EHA, SIOPe), brought together 800 participants in November 2025, with sessions spanning educational, translational, basic and clinical science. Vienna proved to be an ideal location and drew many colleagues from all of Europe and neighbouring countries. We are therefore delighted to return to this setting.

This joint meeting will build on our overlapping interests and consolidate them as common ground. The programme will range from essential infection-specific immunological pathways and their pathological impairment in disease, to infection-triggered autoimmunity and inflammation, often facilitated by underlying errors of immunity. It will also highlight novel targeted and cellular therapeutic strategies.

Three keynote lectures will set the scene:

• Steven Holland (NIH) will speak on CGD and beyond: what infections teach us about immunity.
• Lluis Quintana-Murci (Pasteur Institute) will address the coevolution of pathogens and human immunity.
• Sir Andrew Pollard (Oxford) will discuss how we can be ready for the next pandemic, from fast-track vaccines to the identification of host factors.

The two main days will be split into thematic mornings and afternoons of translational science, and have been designed around the needs of clinicians, bringing laboratory insights to the bedside. Six plenary sessions, each featuring two to three expert speakers and two to three selected abstracts, will cover the key themes of the meeting. Further, an additional half-day of educational sessions will provide a solid foundation for trainees and colleagues new to the field.

This unique programme is being sculpted to offer you take-home value, whether you are a clinician or researcher, from either paediatric and adult medicine, with clinical as well as translational scientific backgrounds. We warmly invite you to join us in Vienna for exchange, learning and new collaborations across disciplines.

We look forward to welcoming you to Vienna.
With warm regards,

Markus Seidel, Interplay 2027 ESID Co-Chair
Maddalena Giannella, Interplay 2027 ESCMID Co-Chair
Olaf Neth, Interplay 2027 ESPID Co-Chair

And the whole scientific committee.