Table 6. Quebec household transmission study: Secondary pH1N1 attack rates among household members by 2008–09 TIV status.

Outcome Category and 2008–09 TIV Status	Children <18 y, N = 48	RR (95% CI) Vaccinated Versus Unvaccinated Children	Adults ≥18 y, N = 72	RR (95% CI) Vaccinated Versus Unvaccinated Adults	Total, N = 120	RR (95% CI) Vaccinated Versus Unvaccinated Overall
Respiratory symptoms
Received TIV	4/8 (50%)	0.71 (0.35–1.47)	13/24 (54%)	0.96 (0.62–1.50)	17/32 (53%)	0.85 (0.59–1.22)
Did not receive TIV	28/40 (70%)	1	27/48 (56%)	1	55/88 (63%)	1
Influenza-like illness (ILI) syndrome
Received TIV	3/8 (38%)	1.00 (0.38–2.66)	8/24 (33%)	3.20 (1.17–8.74)	11/32 (34%)	1.51 (0.82–2.80)
Did not receive TIV	15/40 (38%)	1	5/48 (10%)	1	20/88 (23%)	1
Any PCR-confirmed pH1N1
Received TIV	2/8 (25%)	0.59 (0.17–2.06)	12/24 (50%)	2.18 (1.13–4.20)	14/32 (44%)	1.38 (0.84–2.26)
Did not receive TIV	17/40 (43%)	1	11/48 (23%)	1	28/88 (32%)	1

ILI is defined as fever + cough + one or more of sore throat, myalgia, arthralgia, headache, or prostration.