Detection of influenza vaccine effectiveness among nursery school children: Lesson from a season with cocirculating respiratory syncytial virus

Figures & data

Table 1. Baseline characteristics of vaccinees and nonvaccinees

Characteristics	Vaccinee (N=45)	Nonvaccinee (N=56)	P value^1
Sex (male)	29 (64)	28 (50)	0.146
Age (months)	55.0 (17.5–81.2)	58.6 (12.5–81.1)	0.710
Current body weight (kg)	16.8 (11.0–23.4)	17 (10.7–26.0)	0.940
Underlying illness
any disease	18 (40)	15 (27)	0.159
asthma	13 (29)	4 (7)	0.004
allergy	13 (29)	11 (20)	0.278
Influenza vaccination in previous season (2005–2006)	35 (78)	7 (13)	<0.001
Medical office visit within 6 months for cold-like illness	30 (67)	37 (66)	0.950
Past history of hospitalization	12 (27)	25 (27)	0.950
Sleeping hours	10.0 (8.0–11.0)	9.0 (7.0–11.0)	0.012
Influenza vaccination of family members	36 (80)	21 (38)	<0.001
Number of family members	4 (3–8)	4.5 (2–8)	0.075
Number of siblings	2 (1–4)	2 (1–4)	0.337
Room space per person (m^2)	21.7 (7.03–49.5)	14.7 (6.25–47.0)	0.019
Presence of smoker in the family	34 (76)	31 (55)	0.035

Values are expressed as median (range) or number (%), unless otherwise indicated.

¹Chi-square test or Wilcoxon rank sum test employed where appropriate.

Table 2. Odds ratios of 2006–07 influenza vaccination for outcomes during the entire study period (weeks 1 through 15 of 2007).

	Number (%)		Univariate		Multivariate^1
outcomes	Vaccinee (N=45)	Nonvaccinee (N=56)	OR (95%CI)	P value	OR (95%CI)	P value
Fa	21(47)	37 (66)	0.45 (0.20–1.01)	0.052	1.02 (0.25–4.26)	0.974
FaS	19 (42)	36 (64)	0.41 (0.18–0.91)	0.028	0.291 (0.072–1.143)	0.0762
FaSS	18 (40)	33 (59)	0.47 (0.21–1.03)	0.060	0.289 (0.069–1.142)	0.0761
Fb	16 (36)	23 (41)	0.79 (0.35–1.78)	0.572	0.82 (0.22–2.98)	0.758
FbS	13 (29)	23 (41)	0.58 (0.25–1.35)	0.206	0.285 (0.070–1.141)	0.0759
FbSS	12 (27)	23 (41)	0.52 (0.22–1.23)	0.133	0.286 (0.070–1.140)	0.0758

Note: OR: odds ratio, CI: confidence interval, Fa: fever ≥38.0°C alone, FaS: Fa plus ≥ one respiratory symptoms (rhinorrhea, cough and/or sore throat), FaSS: Fa plus ≥ 2 respiratory symptoms, Fb: ≥39.0°C alone, FbS: Fb plus ≥ one respiratory symptoms, FbSS: Fb plus ≥ 2 respiratory symptoms.

¹Adjusted for age, sex, influenza vaccination of family members, asthma, sleeping hours, number of family members, presence of smoker in the family, 2005–2006 influenza vaccination, room space per person.

Table 3. Odds ratios of 2006–07 influenza vaccination for outcomes during RSV infection epidemic period at nursery school (weeks 1 through 5 of 2007).

	Number (%)		Univariate		Multivariate^1
outcomes	Vaccinee (N=45)	Nonvaccinee (N=56)	OR (95%CI)	P value	OR (95%CI)	P value
Fa	11 (24)	18 (32)	0.68 (0.28–1.65)	0.397	0.65 (0.14–2.91)	0.570
FaS	10 (22)	16 (29)	0.71 (0.29–1.78)	0.469	0.53 (0.11–2.55)	0.432
FaSS	10 (22)	12 (21)	1.05 (0.41–2.71)	0.923	0.82 (0.17–4.05)	0.805
Fb	6 (13)	9 (16)	0.80 (0.26–2.46)	0.701	1.25 (0.20–7.64)	0.813
FbS	5 (11)	6 (16)	0.65 (0.20-2.11)	0.476	0.65 (0.10-4.32)	0.660
FbSS	5 (11)	8 (14)	0.75 (0.23-2.47)	0.637	0.57 (0.08-3.91)	0.566

Note: same as Table 2.

Table 4 Odds ratios of 2006-07 influenza vaccination for outcomes during influenza epidemic period in Fukuoka prefecture (weeks 6 through 14 of 2007).

outcomes	Number (%)		Univariate		Multivariate^1
	Vaccinee (N=45)	Nonvaccinee (N=56)	OR (95%CI)	P value	OR (95%CI)	P value
Fa	15 (33)	30 (54)	0.43 (0.19-0.98)	0.044	0.64 (0.17-2.40)	0.504
FaS	13 (29)	30 (54)	0.35 (0.15-0.81)	0.014	0.31 (0.08-1.19)	0.089
FaSS	11 (24)	26 (46)	0.37 (0.16-0.88)	0.025	0.25 (0.06-1.01)	0.051
Fb	12 (27)	18 (32)	0.77 (0.32-1.83)	0.549	0.53 (0.13-2.11)	0.367
FbS	10 (22)	18 (32)	0.60 (0.25-1.48)	0.271	0.22 (0.05-1.00)	0.050
FbSS	8 (18)	17 (30)	0.50 (0.19-1.29)	0.149	0.20 (0.04-0.94)	0.041

Note: same as Table 2.

Table 5 Odds ratios of 2006-07 influenza vaccination for each outcome during influenza outbreak period at the nursery school (weeks 10 through 14 of 2007).

outcomes	Number (%)		Univariate		Multivariate^1
	Vaccinee (N=45)	Nonvaccinee (N=56)	OR (95%CI)	P value	OR (95%CI)	P value
Fa	13 (29)	29 (52)	0.38 (0.17-0.87)	0.022	0.39 (0.11-1.42)	0.152
FaS	12 (27)	28 (50)	0.36 (0.16-0.85)	0.019	0.23 (0.06-0.91)	0.036
FaSS	10 (22)	25 (45)	0.35 (0.15-0.85)	0.021	0.21 (0.05-0.85)	0.029
Fb	10 (22)	16 (29)	0.71 (0.29-1.78)	0.470	0.32 (0.07-1.48)	0.145
FbS	9 (20)	16 (29)	0.63 (0.25-1.59)	0.323	0.18 (0.04-0.93)	0.041
FbSS	7 (16)	15 (27)	0.50 (0.19-1.37)	0.179	0.16 (0.03-0.87)	0.033

Note: same as Table 2.

Figure 1. (A) Numbers of patients with influenza and RSV infections reported weekly from sentinel hospitals in Fukuoka Prefecture. (B) The cumulative total numbers of patients among the nursery school children classified by the case definitions (Fa: ≥38.0°C alone, FaSS: Fa plus ≥2 respiratory symptoms, Fb: ≥ 39.0°C alone FbSS: Fb plus ≥2 respiratory symptoms). Positive cases confirmed by rapid diagnostic tests for influenza virus and RSV among patients ≥37.5°C are shown as influenza virus:△ and RSV:∘. Four observational periods were defined as follows: period 1, from weeks 1 through 15 of 2007 (the entire observation period); period 2, from weeks 1 through 5 (the period of the outbreak of RSV infection among the nursery school children); period 3, from weeks 6 through 14 (the period of the influenza epidemic in Fukuoka Prefecture); and period 4, from weeks 10 through 14 (the period of the outbreak of influenza among the nursery school children).