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Immune Responses of Healthy Subjects to a Single Dose of Intramuscular Inactivated Influenza A/Vietnam/1203/2004 (H5N1) Vaccine After Priming with an Antigenic Variant


Journal Article

Goji, N.A.; Nolan, C.; Hill, H.; Wolff, M.; Noah, D.L.; Williams, T.B.; Rowe, T.; Treanor, J.J.

J Infec Dis




Adolescent; Adult; Antibodies-Viral; Antigens-Viral; Dose-Response Relationship-Immunologic; Female; Immunization Schedule; Influenza A Virus-H5N1 Subtype; Influenza Vaccines; Influenza-Human; Male; Middle Aged; Vaccines

BACKGROUND: We administered a single dose of influenza A/Vietnam/1203/2004 (H5N1, clade 1) vaccine to subjects who had received 2 doses of influenza A/Hong Kong/156/1997 (H5N1, clade 0) vaccine in 1998. METHODS: Thirty-seven subjects previously vaccinated with a baculovirus-expressed recombinant hemagglutinin A/Hong Kong/156/1997 vaccine in 1998 received a single intramuscular dose of 90 microg of inactivated subvirion A/Vietnam/1203/2004 vaccine in 2006. Serum antibody was measured before vaccination and 28 and 56 days after vaccination. Antibody responses were compared with those measured after one or two 90-microg doses in H5-naive subjects. RESULTS: On day 28 after a single dose, the geometric mean titer (GMT) of hemagglutination-inhibition antibody in primed subjects was 64.0 (95% confidence interval [CI], 37.8-108.5), with 68% responding (4-fold increase in antibody level to a titer of >or=1:40). In contrast, H5-naive subjects who received two 90-microg doses had a day 56 (28 days after the second dose) GMT of 27.7 (95% CI, 20.3-38.0), with only 43% responding. CONCLUSIONS: This study suggests that priming can result in immune responses to a single dose of an antigenically variant strain of H5N1 influenza virus and could be a useful strategy for pandemic control.

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