Table 2. Antibody responses and protection of offspring when both mothers and offspring were immunized 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	11.50±0.58d	12.33±0.58c, d	14.60±0.55c, d	0/9c
	5.0	11.00±0.00c, d	14.25±0.50c, d	13.38±0.28c, d	0/9c
	unimmunized	11.75±0.50d	10.30±0.50d	13.83±0.44d	0/9
Unimmunized	1.0	11.25±0.50d	16.50±0.58d	Undetectedd	9/9d
	5.0	13.50±0.58d	18.50±0.58d	Undetectedd	9/9d
	unimmunized	<1	<1	19.5±0.17	0/9

^a Female mice were immunized twice at a 3 week interval with the inactivated vaccine through the IP route. The offspring were also immunized through the IP route at 1 and 4 weeks of age. Serum samples were collected from the offspring 3 weeks after the primary immunization and 1 week after the booster. Serum IgG Ab titers were measured by ELISA. One week after the booster, the offspring were challenged with a lethal dose (40 LD₅₀) of A/Chicken/Henan/12/2004 (H5N1). Lungs were removed from 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.