Table 3.

Infant Hemagglutination Inhibition Antibody Levels

Timepoint	Subjects, No.	Seroprotectiona (%)	Geometric Mean Titer
		(95% CI)	(95% CI)
Birth	106	65 (55–74)	55 (43–70)
3 mo	97	26 (17–36)b	14 (12–17)c
6 mo	59	12 (5–23)b	13 (11–17)c

Abbreviation: CI, confidence interval.

Infant antibody levels at birth, 3 months, and 6 months were analyzed for those infants with available data whose mothers received both doses of vaccine and delivered subsequent to the 10-day postvaccine dose 2 timepoint.

^a Seroprotection defined as hemagglutination inhibition titer ≥40.

^b P < .0001 (McNemar test) for the comparison to seroprotection at birth.

^c P < .0001 (sign test) for the comparison to geometric mean titer at birth.