Cross-Protective Efficacy of Monovalent Live Influenza B Vaccines against Genetically Different Lineages of B/Victoria and B/Yamagata in Ferrets

Table 3

Virus replication in lungs and upper respiratory tract of ferrets (virus isolation in embryonated eggs).

Group	Vaccination		Challenge
	Vaccine administered	Vaccine virus titer in nasal washes, day 3 (/ml)	WT challenge virus given, day 21	WT challenge virus titer in nasal washes, day 24 (/ml)	WT challenge virus titer in lung tissue, day 24 (/ml per g)
1	B/Vic LAIV	3.88 ± 0.119	B/Vic WT virus	0.90 ± 0.900	< 1.5
2	B/Vic LAIV		B/Yam WT virus	1.67 ± 0.953	< 1.5
3	B/Yam LAIV	3.68 ± 0.120	B/Yam WT virus	0.70 ± 0.700	< 1.5
4	B/Yam LAIV		B/Vic WT virus	1.83 ± 0.970	< 1.5
5	None	n.d.^1	B/Vic WT virus	5.53 ± 0.167	3.01 ± 0.200
6	None	n.d.	B/Yam WT virus	3.70 ± 0.764	0.96 ± 0.957
7	None	< 1.5^2	None	< 1.5	< 1.5

.d.: not determined. ²Estimated threshold limit value.