Immunogenicity of an inactivated monovalent 2009 H1N1 influenza vaccine in pregnant women.
Author(s): Jackson LA, Patel SM, Swamy GK, Frey SE, Creech CB, Munoz FM, Artal R, Keitel WA, Noah DL, Petrie CR, Wolff M, Edwards KM
Affiliation(s): The Group Health Research Institute, Group Health, Seattle, Washington, USA. firstname.lastname@example.org
Publication date & source: 2011-09-15, J Infect Dis., 204(6):854-63.
Publication type: Randomized Controlled Trial; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't
BACKGROUND: Although pregnant women are at increased risk of severe illness following influenza infection, there is relatively little information on the immunogenicity of influenza vaccines administered during pregnancy. METHODS: We conducted a clinical trial that enrolled 120 pregnant women in which participants were randomly assigned to receive an inactivated 2009 H1N1 influenza vaccine containing either 25 mug or 49 mug of hemagglutinin (HA) in a 2-dose series with a 21-day period between administration of the first and second doses. RESULTS: Following the first vaccination, HA inhibition (HAI) titers of >/=1:40 were detected in 93% (95% confidence interval [CI], 82%-98%) of subjects who received the 25-mug dose and 97% (95% CI, 88%-100%) of subjects receiving the 49-mug dose. In cord blood samples, HAI titers of >/=1:40 were found in 87% (95% CI, 73%-96%) of samples from the 25-mug dose group and in 89% (95% CI, 76%-96%) from the 49-mug dose group. Microneutralization titers tended to be higher than HAI titers, but the patterns of response were similar. CONCLUSIONS: In pregnant women, 1 dose of an inactivated 2009 H1N1 influenza vaccine containing 25 mug of HA elicited an antibody response typically associated with protection against influenza infection. Efficient transplacental transfer of antibody was also documented.