TABLE 2.

Distribution of invasive Haemophilus influenzae type b isolates from cases of vaccine failures and controls in the United Kingdom (1991 to 2003) into PFGE clusters

PFGE cluster	No. (%) of strains		OR (95% CI)	Pa
	Vaccine failure	Control
Type I	156 (41.3)	193 (51.3)	1.90 (0.8-4.4)	0.16
Type II	4 (1.1)	12 (3.1)	0.42 (0.13-1.3)	0.19
Type III	0 (0)	7 (2.1)	0.08 (0.004-1.4)	0.02
Type IV	4 (1.1)	0 (0)	11.92 (0.63-223.1)	0.03
Total	164 (43.5)	212 (56.5)

^aBy Fisher's exact test.