1. Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, New York, USA
2. Norwegian Institute of Public Health, Oslo, Norway
3. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA
4. New York State Psychiatric Institute, New York, New York, USA
5. Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, New York, USA
6. Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway
7. KG Jebsen Center for Influenza Vaccine Research, Oslo, Norway