1 Department of Immunology, Oslo University Hospital Rikshospitalet and University of Oslo, Oslo, Norway.
2 Department of Genetics, Cell and Immunobiology, Semmelweis University, Budapest, Hungary.
3 K. G. Jebsen Center for Influenza Vaccine Research, Institute of Immunology, University of Oslo and Oslo University Hospital, Oslo, Norway.
4 Department of Medicine, Institute of Clinical Medicine, Helsinki University Central Hospital and ORTON Orthopaedic Hospital of the Invalid Foundation, Helsinki, Finland.