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.
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.


BACKGROUND
ClinicalTrials.gov identifier: NCT00240903.
Goji
Nega Ali
NA
University of Rochester Medical Center, Rochester, New York 14642, USA.
Nolan
Carrie
C
Hill
Heather
H
Wolff
Mark
M
Noah
Diana L
DL
Williams
Tracy B
TB
Rowe
Thomas
T
Treanor
John J
JJ
D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000096:biosynthesis / Q000097:blood; D000956:Antigens, Viral / Q000145:classification* / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology
D000914:Antibodies, Viral; D000956:Antigens, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated