CIRI-IT	Interuniversity Research Center on Influenza and other Transmissible Infections
COVID-19	Coronavirus disease 2019
DRIVE	Development of Robust and Innovative Vaccine Effectiveness
ECDC	European Centre for Disease Prevention and Control
EMA	European Medicines Agency
EU	European Union
FISABIO	Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunitat Valenciana
GP	General practice
GTPUH	Germans Trias I Pujol University Hospital
HUS	Helsinki University Hospital, Jorvi Hospital
HUVH	Hospital Universitari Vall D’Hebron
ICU	Intensive care unit
ILI	Influenza-like illness
IMI	Innovative Medicines Initiative
IREIVAC	Innovative Clinical Research Network in Vaccinology
IVE	Influenza vaccine effectiveness
LCI	Lab-confirmed influenza
LPUH	La Paz University Hospital
MUV	Medical University Vienna
NIID	National Institute for Infectious Disease “Prof. Dr. Matei Bals”
PPE	Personal protective equipment
RSV	Respiratory syncytial virus
RT-PCR	Reverse-transcriptase polymerase chain reaction
SAP	Statistical analysis plan
SARI	Severe acute respiratory illness
SARS-CoV-2	Severe acute respiratory syndrome coronavirus 2
TND	Test-negative design
VAHNSI	Valencia Hospital Surveillance Network for the Study of Influenza and Respiratory Viruses Disease