Table 5. Antibody responses and protection of offspring when mothers were immunized via the IN route and their offspring via the IP route^a.

Mothers	Vaccine dosage for offspring (μg)	Serum IgG Ab titers in offspring (log2)b		Lung virus titers (log10 TCID50) b	Survival offspring/tested offspring
		Prime	Boost
Immunized	1.0	11.00±0.00	12.67±0.58c,d	13.57±0.83c,d	0/9c
	5.0	10.67±0.58	13.00±0.00c,d	12.78±0.69c,d	1/9c
	unimmunized	12.25±0.50	10.00±1.00d	13.72±0.26d	0/9
Unimmunized	1.0	11.50±0.58	16.50±0.58	Undetected	9/9d
	5.0	13.50±0.58	18.50±0.58	Undetected	9/9d
	unimmunized	<1	<1	18.33±0.33	0/9

^a Female mice were immunized twice at a 3 week interval with the inactivated vaccine through the IN route. The offspring were immunized through the IP route at 1 and 4 weeks of age. One week after the booster, the offspring were challenged with a lethal dose (40 LD₅₀) of A/Chicken/Henan/12/2004 (H5N1). Serum samples were collected from the offspring 3 weeks after the primary immunization and 1 week after the booster. Serum IgG antibody titers were measured by ELISA. Lungs were removed from at least three mice in each group 3 days after challenge for virus titration by the standard MDCK assay. Survival rates of the mice were determined 3 weeks after the challenge.

^b Values represent the mean ± S.D. of each group.

^c Significant difference (p <0.05) compared with the same dosage group of offspring without MDAs.

^d Significant difference (p <0.05) compared with the negative control