Table 4. Association between a history of PPV23 and influenza vaccination and influenza hospitalization.

Influenza vaccine + PPV23	Casesa vaccinated/N (%)	Controls vaccinated/N (%)	Crude OR (95% CI)	Adjusted ORb (95% CI)	Adjusted Vaccination Effectiveness (95% CI)
All patients
With Risk Conditions	23/813 (2.8%)	105/1610 (6.5%)	0.30 (0.18–0.52)	0.19 (0.09–0.38)	81% (62–91)c
All	23/1051 (2.2%)	118/2068 (5.7%)	0.26 (0.15–0.45)	0.19 (0.10–0.35)	81% (65–90)d
18–64 y
With Risk Conditions	5/618 (0.8%)	26/1196 (2.2%)	0.27 (0.09–0.80)	0.19 (0.06–0.65)	81% (35–94)e
All	5/834 (0.6%)	31/1602 (1.9%)	0.23 (0.08–0.66)	0.16 (0.05–0.52)	84% (48–95)f
≥ 65 y
With Risk Conditions	18/195 (8.3%)	79/414 (19.1%)	0.38 (0.20–0.74)	0.24 (0.10–0.60)	76% (40–90)g
All	18/217 (8.3%)	87/466 (18.7%)	0.33 (0.17–0.63)	0.24 (0.10–0.54)	76% (46–90)h

Abbreviations: OR, odds ratio; CI, confidence interval. ^aLaboratory-confirmed by RT-PCR. ^bAdjusted for: With Risk Conditions: Age, sex (only for ≥ 65y), smoker, alcoholism (only for ≥ 65y), pneumonia, COPD (only for all patients and 18–64y), asthma (only for all patients and 18–64y), cardiovascular disease (only for all patients and 18–64y), diabetes (only for all patients and 18–64y), HIV infection (only for all patients and 18–64y), neurological disease (only for all patients and 18–64y), neoplasia (only for all patients and 18–64y), transplantation, previous antibiotics, corticosteroids. All: Age, ethnicity (only for all patients and 18–64y), smoker (only for all patients and ≥ 65y), pneumonia, COPD, asthma (only for all patients and 18–64y), diabetes (only for all patients and 18–64y), HIV infection (only for all patients and 18–64y), neurological disease (only for all patients and 18–64y), transplantation, previous antibiotics, corticosteroids. Hosmer-Lemeshow test: ^cp = 0.89; ^dp = 0.39; ^ep = 0.49; ^fp = 0.36; ^gp = 0.52; ^hp = 0.43