Table 2.

Risk of RSV-related mechanical ventilation in Danish children aged younger than 5 years with RSV

	Children who required mechanical ventilation, n*		Risk of mechanical ventilation per 100 000 population (95% CI)			Risk of mechanical ventilation per 1000 RSV-associated hospital admissions (95% CI)
	2016–17 to 2019–20	2021–22	2016–17 to 2019–20	2021–22	RR (95% CI)†; p value‡	2016–17 to 2019–20	2021–22	RR (95% CI)†; p value‡
Total	76	43	6·1 (4·8–7·7)	13·9 (10·0–18·7)	2·3 (1·6–3·3); p<0·0001	12·9 (10·1–16·1)	14·3 (10·4–19·3)	1·1 (0·8–1·6); p=0·559
<3 months	37	20	59·8 (42·1–82·5)	129 (79·0–199·7)	2·2 (1·3–3·7); p=0·007	17·5 (12·3–24·0)	17·2 (10·5–26·5)	1·0 (0·6–1·7); p=1·000
3–5 months	6	2	9·7 (3·6–21·1)	13·0 (1·6–46·7)	1·3 (0·3–6·7); p=0·664	5·6 (2·0–12·1)	5·0 (0·6–17·8)	0·9 (0·2–4·4); p=1·000
6–11 months	9	4	7·3 (3·3–13·8)	12·9 (3·5–33·1)	1·8 (0·6–5·8); p=0·308	9·1 (4·2–17·3)	10·9 (3·0–27·7)	0·9 (0·2–3·3); p=1·000
12–17 months	10	4	8·1 (3·9–14·9)	12·9 (3·5–33·1)	1·6 (0·5–5·1); p=0·500	11·3 (5·4–20·7)	10·1 (2·8–25·7)	0·9 (0·3–2·8); p=0·764
18–23 months	7	5	5·7 (2·3–11·7)	16·2 (5·2–37·7)	2·9 (0·9–9·0); p=0·073	16·1 (6·5–33·1)	20·3 (6·6–46·8)	1·3 (0·4–4·0); p=1·000
24–59 months	7	8	0·9 (0·4–1·9)	4·3 (1·8–8·4)	4·6 (1·7–12·6); p=0·004	17·0 (6·9–34·7)	18·8 (8·1–36·7)	1·1 (0·4–3·0); p=1·000

RSV=respiratory syncytial virus. RR=risk ratio.

^*The total number of children who received mechanical ventilation was 133; 54 in 2021–22 identified by prospective enrollment and 15–28 annually in 2016–17 to 2019–20 identified by the Danish National Patient Registry; to compare the risk of mechanical ventilation in children younger than 5 years between seasons, only patients identified through the Danish National Patient Registry were included (n=43 in 2021–22 and n=76 in 2016–17 to 2019–20). Five children aged older than 5 years were excluded (n=3 in 2016–17 to 2019–20; n=2 in 2021–22).

^‡p values derived from Fisher's exact test.