1. Hygiene Unit, San Martino Policlinico Hospital-IRCCS for Oncology and Neurosciences, 16132 Genoa, Italy
2. SWG S.p.A., 34133 Trieste, Italy
3. CSL Seqirus, 53035 Monteriggioni, Italy
4. Department of Life Sciences, University of Siena, 53100 Siena, Italy
5. Department of Health Sciences (DISSAL), University of Genoa, 16132 Genoa, Italy
6. Interuniversity Research Center on Influenza and Other Transmissible Infections (CIRI-IT), 16132 Genoa, Italy