Multi-Centre Observational Study of Transplacental Transmission of Influenza Antibodies following Vaccination with AS03(A)-Adjuvanted H1N1 2009 Vaccine

Introduction: Illness and death from influenza increase during pregnancy. In the United Kingdom pregnant women were targeted in a national programme for vaccination during the H1N1 2009–10 pandemic. Methods: In this study, pregnant women were recruited in labour from November 9, 2009 to March 10, 2010. Pandemic vaccination status was determined. Venous cord blood collected at delivery was evaluated for transplacental transfer of antibodies by measurement of haemagglutination inhibition and microneutralization titres. Results: Samples were collected from 77 vaccinated and 27 unvaccinated women. Seroprotection (HI titre ≥1:40) was detected in 58 (75.3%, 95% CI 64.2–84.4) cord blood samples from vaccinated women and 5 (18.5%, 95% CI 6.3–38.1) from unvaccinated women (P<0.0001). There was evidence of transplacental seroprotection 8 days after maternal immunization (77.9%, 95 CI 66.2–87.1), maintained in most cases for at least 16 weeks. Discussion: Immunization of pregnant women with AS03A-adjuvanted vaccine is followed by transplacental transfer of passive immunity at titres consistent with clinical protection in three-quarters of new-born infants. The findings support national and international pandemic H1N1 2009 recommendations for immunization during pregnancy

Multi-Centre Observational Study of Transplacental Transmission of Influenza Antibodies following Vaccination with AS03_A-Adjuvanted H1N1 2009 Vaccine

<div><h3>Introduction</h3><p>Illness and death from influenza increase during pregnancy. In the United Kingdom pregnant women were targeted in a national programme for vaccination during the H1N1 2009–10 pandemic.</p> <h3>Methods</h3><p>In this study, pregnant women were recruited in labour from November 9, 2009 to March 10, 2010. Pandemic vaccination status was determined. Venous cord blood collected at delivery was evaluated for transplacental transfer of antibodies by measurement of haemagglutination inhibition and microneutralization titres.</p> <h3>Results</h3><p>Samples were collected from 77 vaccinated and 27 unvaccinated women. Seroprotection (HI titre ≥1∶40) was detected in 58 (75.3%, 95% CI 64.2–84.4) cord blood samples from vaccinated women and 5 (18.5%, 95% CI 6.3–38.1) from unvaccinated women (P<0.0001). There was evidence of transplacental seroprotection 8 days after maternal immunization (77.9%, 95 CI 66.2–87.1), maintained in most cases for at least 16 weeks.</p> <h3>Discussion</h3><p>Immunization of pregnant women with AS03_A-adjuvanted vaccine is followed by transplacental transfer of passive immunity at titres consistent with clinical protection in three-quarters of new-born infants. The findings support national and international pandemic H1N1 2009 recommendations for immunization during pregnancy.</p> </div

Boxplot GMT haemagglutinination inhibition titre by interval from maternal vaccination to delivery.

<p>(Titres are expressed as reciprocal of the dilution and are given on a log₂ scale.).</p

Reverse cumulative distribution curves of haemagglutinination inhibition and microneutralization antibody titres in cord blood serum samples.

<p>(Titres are expressed as reciprocal of the dilution and are given on a log₂ scale.) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047448#pone.0047448-Puleston1" target="_blank">[33]</a>.</p

Scatter-plots for cord blood haemagglutinination inhibition and microneutralization titres against interval between vaccination and delivery.

<p>(Titres are expressed as reciprocal of the dilution and are given on a log₂ scale.).</p

Baseline characteristics of vaccinated and unvaccinated mothers [33].

<p>Data are means for: years/birth weight/gestational age (95% confidence interval) or number (%) for all other parameters.</p