Table 2.

Risk factors for hospitalization in notified pertussis cases for infants in South Australia

Infants <1 year (n = 132)	Hospitalization requirement		χ2 test P value	Relative risk for hospitalization (95% CI)
Nil or unknown hospital requirements	Hospitalized
Age (months)
<2	9	19	P < 0·001	2·3 (1·60–3·32)
2 to <12	71	33
Gender
Male	49	26	P = 0·202	1·1 (0·87–1·43)
Female	31	26
Ethnicity
Indigenous	4	7	P = 0·09	1·7 (1·03–2·83)
Non-Indigenous	76	45
Pertussis vaccine*
0–1 dose	45	40	P = 0·001	4·1 (1·37–12·11)
2–3 doses	23	3

CI, Confidence interval.

^*Those without evidence of vaccination were considered unknown and excluded in this analysis.