. 2022 Jan 19;16(4):632–642. doi: 10.1111/irv.12955

TABLE 1.

Rate of hospitalization for adults aged 50–64 or 45–64 years with laboratory confirmed influenza, 2010–2011 to 2019–2020 influenza seasons

								Hospitalization rate (per 100,000)
First author, year of publication	Country (Data source)	Population	Indication for testing	Included admission diagnosis	Season(s)	Number of hospital inpatients	Population size	Crude	Adjusted ^a	Dominant influenza strain
CDC, 2020 ⁴² and Tokars, 2018 ²⁴	United States (FluSurv‐NET)	50–64 years	Clinician's discretion	Any	2010–11	1205	5,499,620	21.9	86.1	A(H3N2)
					2011–12	432	5,346,197	8.1	33.1	A(H3N2)
					2012–13	2210	5,430,213	40.7	151.7	A(H3N2)
					2013–14	2845	5,296,266	53.7	137.9	A(H1N1)
					2014–15	2871	5,372,656	53.4	137.2	A(H3N2)
					2015–16	2450	5,372,656	45.1	117.1	A(H1N1)
					2016–17	N/A	N/A	62.7		A(H3N2)
					2017–18	N/A	N/A	112.8		A(H3N2)
					2018–19	N/A	N/A	79.2		A(H3N2)
					2019–20	N/A	N/A	89.4		A(H3N2)
Hughes, 2019 ²⁵	United States, Utah	50–64 years	Clinician's discretion	Any	2016–17	N/A	N/A	56	91	N/A
Hughes, 2019 ²⁵	United States, Utah	50–64 years	Clinician's discretion	Any	2017–18	N/A	N/A	87	142	N/A
Leng, 2018 ²⁶	Cambodia	50–64 years	SARI ^b	Not described	2015	5	30,991	16.1		A(H3N2)
Leng, 2018 ²⁶	Cambodia	50–64 years		Not described	2016	28	62,290	44.9		A(H1N1) & B
Yu, 2014 ²⁷	China	45–64 years	SARI ^c	Not described	2010–11	134	224,903	60		N/A
Yu, 2014 ²⁷	China	45–64 years	SARI ^c	Not described	2011–12	56	224,903	25		N/A
PHAC, 2020 ⁴³	Canada (FluWatch)	45–64 years	Clinician's discretion	Symptoms compatible with influenza	2013–14	N/A	N/A	29		A(H1N1)
					2014–15	N/A	N/A	16		A(H3N2)
					2015–16	N/A	N/A	37		A(H1N1)
					2016–17	N/A	N/A	22		A(H3N2)
					2017–18	N/A	N/A	41		A(H3N2)
					2018–19	N/A	N/A	40		A(H1N1)
					2019–20	N/A	N/A	23		A(H1N1)

Abbreviations: CDC, Centre for Disease Control and Prevention; ICD‐10, International Classification of Diseases Tenth Revision; N/A, not available; PHAC, Public Health Agency of Canada; SARI, severe acute respiratory illness.

^{^a}

Tokars and Hughes adjusted rates for the age group‐specific percentage of hospital inpatients with respiratory disease that were tested for influenza and the sensitivity and specificity of laboratory methods used.

^{^b}

Fever or history of fever (≥38°C), cough or sore throat, and shortness of breath or difficulty breathing in a hospitalized person with onset of symptoms within 10 days before hospitalization.

^{^c}

Rectal or axillary temperature ≥37.3°C and at least one of cough, sore throat, tachypnea, difficulty breathing, abnormal breath sounds on auscultation, sputum production, hemoptysis, chest pain, or chest radiograph consistent with pneumonia.