A single dose of unadjuvanted novel 2009 H1N1 vaccine is immunogenic and well tolerated in young and elderly adults.
BACKGROUND
When the novel H1N1 influenza A strain appeared in April of 2009, development of novel H1N1 vaccines became a public health priority.


METHODS
We conducted a phase‐2, multicenter, randomized, placebo‐controlled, observer‐blind clinical trial of a 2009 H1N1 vaccine in 1313 young (age, 18-64 years) and older (age, >or=65 years) adults. Participants were randomized 1:4:4:4 to receive 2 doses of placebo or 7.5, 15, or 30 μg of H1N1 hemagglutinin administered 21 days apart. In post hoc analyses, hemagglutination inhibition (HI) titers measured at baseline and after vaccination were analyzed for young adults (age, 18-64 years), "younger elderly" adults (age, 65-74 years), and "very elderly" adults (age, >or=75 years).


RESULTS
At baseline, 28.8% of young adults, 43.9% of younger elderly adults, and 62.9% of very elderly adults had HI titers to A/2009 H1N1 of >or=1:40. A single 7.5‐μg dose induced HI titers >or=1:40 in 94.5% (95% confidence interval [CI], 91.8%-96.3%) of all adults. After one 7.5‐μg dose, the geometric mean titers achieved were 326.4 (95% CI, 275.9-386.0) in young adults, 155.4 (95% CI, 123.4-195.8) in "younger elderly" adults, and 243.9 (95% CI, 167.1-356.0) in "very elderly" adults.


CONCLUSIONS
This large phase-2 trial demonstrated that a single 7.5‐μg dose of a monovalent unadjuvanted H1N1 vaccine induced protective HI antibody levels in adults of all ages, including very elderly adults.


BACKGROUND
Clinicaltrials.gov identifier NCT00958126.
Talaat
Kawsar R
KR
Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA. ktalaat@jhsph.edu
Greenberg
Michael E
ME
Lai
Michael H
MH
Hartel
Gunter F
GF
Wichems
Christine H
CH
Rockman
Steven
S
Jeanfreau
Robert J
RJ
Ghosh
M Rita
MR
Kabongo
Martin L
ML
Gittleson
Charmaine
C
Karron
Ruth A
RA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007117:Immunization, Secondary / Q000379:methods; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000009:adverse effects* / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010919:Placebos / Q000008:administration & dosage; D014611:Vaccination / Q000379:methods; D055815:Young Adult
D000914:Antibodies, Viral; D007252:Influenza Vaccines; D010919:Placebos