Table 3.

Effect of influenza vaccination status in the current and 5 prior seasons in preventing laboratory-confirmed influenza among patients with chronic obstructive pulmonary disease by (sub)type and presence of other major chronic conditions.

	Cases/controls	Vaccination effect, % (95% CI)a	p value
A/H1N1 subtypeb
Never vaccinated	67/182	Reference
Vaccination in prior seasons only	20/135	47 (5 to 71)	0.034
Current season vaccination	102/721	49 (23 to 66)	0.001
A/H3N2 subtype c
Never vaccinated	56/158	Reference
Vaccination in prior seasons only	37/124	6 (–61 to 44)	0.830
Current season vaccination	139/579	28 (–8 to 52)	0.116
B type d
Never vaccinated	32/127	Reference
Vaccination in prior seasons only	21/106	6 (–93 to 54)	0.867
Current season vaccination	66/517	52 (14 to 73)	0.013
Codiagnosis of asthma
Never vaccinated	14/11	Reference
Vaccination in prior seasons only	6/15	46 (–196 to 90)	0.473
Current season vaccination	30/64	67 (–13 to 90)	0.077
No codiagnosis of asthma
Never vaccinated	140/204	Reference
Vaccination in prior seasons only	73/157	22 (–14 to 47)	0.198
Current season vaccination	279/768	39 (19 to 54)	0.001
Patients with other major chronic conditions
Never vaccinated	93/143	Reference
Vaccination in prior seasons only	63/129	21 (–20 to 48)	0.271
Current season vaccination	243/675	42 (20 to 58)	0.001
Patients without other major chronic conditions
Never vaccinated	61/72	Reference
Vaccination in prior seasons only	16/43	31 (–51 to 68)	0.353
Current season vaccination	66/157	26 (–30 to 58)	0.297

CI confidence interval.

^aVaccination effect adjusted by age groups (25–64, 65–84 and ≥ 85 years), other major chronic conditions, healthcare setting (primary healthcare or hospital), and month-season of sample collection.

^bPooled A/H1N1 analysis includes 2015–2016, 2017–2018, 2018–2019 and 2019–2020 seasons.

^cPooled A/H3N2 analysis includes 2015–2016, 2016–2017, 2017–2018 and 2018–2019 seasons.

^dPooled B analysis includes 2015–2016, 2017–2018 and 2019–2020 seasons.