Table 2.

HAI antibody responses to MVA PR8 HA vaccine were similar to sublethal infection by PR8 virus, neither of which could be boosted by further exposure to MVA HA vaccine or INFV A challenge. Initial exposure to virus or MVA HA(PR8) vaccine resulted in weak HAI titers (column #1) that were boosted by re-administration (column #2). HAI titers were not boosted further (column #3) by additional exposure to MVA HA (PR8) vaccine or lethal PR8 viral challenge. Antibody responses were measured as hemagglutination inhibition (HAI) titers. The HAI test used PR8 influenza virus. Group mean HAI titers are shown over two experiments.

Immunization or Challenge →	1	2	3
Experiment One: two administrations of sublethal INFV A followed by sublethal INFV A or lethal INFV A	Sublethal Influenza N = 25 mice HAI titer = 436 ± 141	Sublethal Influenza N = 25 mice HAI titer = 1173 ± 478	Sublethal Influenza N = 5 mice HAI titer = 1440 ± 556
			Lethal Challenge N = 16 HAI titer = 1307 ± 596
Experiment Two: two administrations of MVA HA vaccine, followed by MVA HA or lethal INFV A	MVA HA N = 25 mice HAI titer = 128 ± 535	MVA HA N = 25 mice HAI titer = 1182 ± 653	MVA HA N = 5 mice HAI titer = 981 ± 324
			Lethal Challenge N = 16 HAI titer = 953 ± 458