Refernece	Objective	Study design	Evidence level
Demicheli et al. [525]	To study the effectiveness of influenza vaccination in persons 14–64 years of age	SR	1A+
Hak et al. [512]	To study the effectiveness of influenza vaccination in adult and elderly high‐risk persons	CCS	4A+
Hak et al. [513] [2]	To study the effectiveness of influenza vaccination in adults 18–64 with COPD	CCS	4A+
Jackson et al. [516]	To study the effectiveness of influenza vaccination in elderly persons	RCS	4A+
Thomas et al. [526]	To study the effectiveness of influenza vaccination of health‐care workers in order to protect elderly persons	SR	1A−
Squarcione et al. [528]	To study the immunogenicity and reactogenicity of inactivated influenza vaccine in older persons	RCT	2C−
Wang et al. [522]	To study live attenuated vs. inactivated influenza vaccines and medical encounters for respiratory illnesses among US military personnel	PCS	3B+
Monto et al. [523]	Comparative efficacy of inactivated and live attenuated influenza vaccines in healthy adults	RCT	2A+
Nichol et al. [524]	To study the effectiveness of influenza vaccination in prevention of influenza‐like illness	PCS	3B+
Schembri et al. [514]	To study the effectiveness of influenza vaccination in prevention of all‐cause mortality in elderly persons	RCS	4A+
Örtqvist et al. [515]	To study the effectiveness of influenza vaccination in prevention of all‐cause mortality in elderly persons	PCS	3A+
Eurich et al. [517]	To study the effectiveness of influenza vaccination in prevention of all‐cause mortality in elderly persons	PCS	3A+
Jackson et al. [518]	To study the effectiveness of influenza vaccination in prevention of community‐acquired pneumonia in immunocompetent elderly people	CCS	4A+
Jefferson et al. [519]	To study vaccines for preventing influenza in the elderly	SR	1B−
Thomas et al. [527]	To study the effect of influenza vaccination for healthcare workers who work with the elderly	SR	1B−