Table 3.

Protective effects in chickens immunized with YX10p75, YX10p90, YX10p102 or H120 against challenge with virulent YX10p5.

Group	Vaccination at day 14	Dosagea (EID50)	Challenge at day 28b	Morbidity	Mortality	Protected	Positive rate of ELISA antibodyc
							14 d post-vaccination	14 d post-challenge
1	p75	103.5	Yes	0/12	0/12	12/12	3/12	9/12
2	p90	103.5	Yes	0/12	0/12	12/12	2/12	6/12
3	p102	103.5	Yes	5/12	1/12	7/12	1/12	6/11
Vaccine	H120	103.5	Yes	9/12	3/12	3/12	1/12	9/9
Positive control	PBS	NA	Yes	12/12	6/12	0/12	0/12	2/6
Negative control	PBS	NA	No	0/12	0/12	12/12	0/12	0/12

^aFourteen-day-old SPF chickens were inoculated with one dose of IBV (passaged virus 10^3.5 EID₅₀/bird or vaccine strain H120 10^3.5 EID₅₀/bird) via the intraocular route.

^bTwo weeks after vaccination, chickens were challenged with IBV YX10p5 at 10^5.5 EID₅₀/bird via the intranasal route.

^cNumber seroconverted/number inoculated.