Table. Association between asymptomatic carriage status for W135 ST-2881 strains in May 2003 and protective immunity to the local strain in February 2004, in persons without protective immunity in May 2003*.

Carrier of W135 strain, May 2003	Protective immunity to W135 ST-2881, February 2004		Total
	No (%)	Yes (%)
No	26 (78.8)	7 (21.2)	33
Yes	6 (46.2)	7 (53.8)	13
Total	32	14	46

*According to serum bactericidal antibody assay; Fisher exact test, p = 0.04; ST, sequence type.