Safety and immune responses in children after concurrent or sequential 2009 H1N1 and 2009-2010 seasonal trivalent influenza vaccinations.
BACKGROUND
Administering 2 separate vaccines for seasonal and pandemic influenza was necessary in 2009. Therefore, we conducted a randomized trial of monovalent 2009 H1N1 influenza vaccine (2009 H1N1 vaccine) and seasonal trivalent inactivated influenza vaccine (TIV; split virion) given sequentially or concurrently in previously vaccinated children.


METHODS
Children randomized to 4 study groups and stratified by age received 1 dose of seasonal TIV and 2 doses of 2009 H1N1 vaccine in 1 of 4 combinations. Injections were given at 21-day intervals and serum samples for hemagglutination inhibition antibody responses were obtained prior to and 21 days after each vaccination. Reactogenicity and adverse events were monitored.


RESULTS
All combinations of vaccines were safe in the 531 children enrolled. Generally, 1 dose of 2009 H1N1 vaccine and 1 dose of TIV, regardless of sequence or concurrency of administration, was immunogenic in children ≥ 10 years of age; children <10 years of age required 2 doses of 2009 H1N1 vaccine.


CONCLUSIONS
Vaccines were generally well tolerated. The immune responses to 2009 H1N1 vaccine were adequate regardless of the sequence of vaccination in all age groups but the sequence affected titers to TIV antigens. Two doses of 2009 H1N1 vaccine were required to achieve a protective immune response in children <10 years of age.


BACKGROUND
NCT00943202.
Division of Infectious Diseases, Allergy and Immunology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA. freyse@slu.edu
Sharon E
SE
Frey
David I
DI
Bernstein
Michael A
MA
Gerber
Harry L
HL
Keyserling
Flor M
FM
Munoz
Patricia L
PL
Winokur
Christine B
CB
Turley
Richard E
RE
Rupp
Heather
H
Hill
Mark
M
Wolff
Diana L
DL
Noah
Allison C
AC
Ross
Gretchen
G
Cress
Robert B
RB
Belshe
D000293:Adolescent; D000375:Aging; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology*; D009981:Influenza B virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology; D008297:Male; D012621:Seasons
D000914:Antibodies, Viral; D007252:Influenza Vaccines