Repeated vaccination is required to optimize seroprotection against H1N1 in the immunocompromised host.
BACKGROUND
In 2009 the declaration by the World Health Organization of a global pandemic of influenza-H1N1 virus led to a vaccination campaign to ensure protection for immunocompromised patients. The goal of this study was to determine the efficacy of the 2009 H1N1 vaccine in patients with hematologic malignancies.


METHODS
We evaluated humoral and cellular immune responses to 2009 H1N1 vaccine in 97 adults with hematologic malignancies and compared these responses with those in 25 adult controls. Patients received two injections of vaccine 21 days apart and the controls received one dose. Antibody titers were measured using a hemagglutination-inhibition assay on days 0, 21 and 49 after injection of the first dose. Cellular immune responses to H1N1 were determined on days 0 and 49.


RESULTS
By day 21 post-vaccination, protective antibody titers of 1:32 or more were seen in 100% of controls compared to 39% of patients with B-cell malignancies (P<0.001), 46% of allogeneic stem cell transplant recipients (P<0.001) and 85% of patients with chronic myeloid leukemia (P=0.086). After a second dose, seroprotection rates increased to 68%, (P=0.008), 73%, (P=0.031), and 95% (P=0.5) in patients with B-cell malignancies, after allogeneic stem cell transplantation and with chronic myeloid leukemia, respectively. On the other hand, T-cell responses to H1N1 vaccine were not significantly different between patients and controls.


CONCLUSIONS
These data demonstrate the efficacy of H1N1 vaccine in most patients with hematologic malignancies and support the recommendation for the administration of two doses of vaccine in immunocompromised patients. These results may contribute towards the development of evidence-based guidelines for influenza vaccination in such patients in the future.
Department of Haematology, Imperial College, Hammersmith Campus, 4th Floor Commonwealth Building, Du Cane Road, London W12 0NN, UK.
Hugues
H
de Lavallade
Paula
P
Garland
Takuya
T
Sekine
Katja
K
Hoschler
David
D
Marin
Kate
K
Stringaris
Eva
E
Loucaides
Katherine
K
Howe
Richard
R
Szydlo
Ed
E
Kanfer
Donald
D
Macdonald
Peter
P
Kelleher
Nichola
N
Cooper
Ahmad
A
Khoder
Ian H
IH
Gabriel
Dragana
D
Milojkovic
Jiri
J
Pavlu
John M
JM
Goldman
Jane F
JF
Apperley
Katayoun
K
Rezvani
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D016022:Case-Control Studies; D005260:Female; D006385:Hemagglutination Inhibition Tests; D019337:Hematologic Neoplasms / Q000276:immunology / Q000628:therapy / Q000821:virology*; D006801:Humans; D007111:Immunity, Cellular; D016867:Immunocompromised Host; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology* / Q000627:therapeutic use*; D007251:Influenza, Human / Q000150:complications / Q000276:immunology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D033581:Stem Cell Transplantation; D015996:Survival Rate; D014611:Vaccination / Q000706:statistics & numerical data*; D055815:Young Adult
D000914:Antibodies, Viral; D007252:Influenza Vaccines