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28-06-2011 | Gynaecology | Article

Flu vaccine during pregnancy can protect newborns


Free abstract

MedWire News: Infants whose mothers receive an influenza vaccination during pregnancy are less likely to be hospitalized for influenza during the first 6 months of life than infants whose mothers receive no vaccination, show study results.

The findings support the current US recommendations from the Advisory Committee on Immunization Practices for influenza vaccination for pregnant women, say the researchers.

"It is recommended that all pregnant women receive the influenza vaccine during pregnancy because it is known that pregnant women have increased morbidity and mortality during pregnancy and in the immediate postpartum period if they get the 'flu," said lead author Katherine Poehling (Wake Forest University School of Medicine, Winston-Salem, North Carolina USA).

"We also know that mothers pass antibodies through the placenta to the baby. This study showed us that receiving the influenza vaccine during pregnancy not only protects the mother, but also protects the baby in the early months of life," she added.

The study cohort comprised 1510 infants aged less than 6 months old who were hospitalized during 2002-2009 for respiratory symptoms and/or fever. A total of 151 (10%) had laboratory-confirmed influenza, with 136 (90%) and 15 (10%) of these cases representing influenza A and B, respectively.

In all, 294 (19%) mothers reported receiving the influenza vaccine during pregnancy with nonsmokers and those who breastfed being the most likely to report vaccination.

Eighteen (12%) of all influenza-positive infants' mothers reported vaccination during pregnancy, whilst 276 (20%) mothers of influenza-negative infants were vaccinated, giving an odds ratio of 0.53.

An initial analysis adjusted for variables including babies' age, sex, race/ethnicity, treatment site, and influenza season, showed that the chances of having an influenza-positive hospitalized infant was 45% less among vaccinated mothers compared with unvaccinated mothers.

Further adjustment for prematurity and high-risk conditions rendered the same reduction in odds, and accounting for exposure to smoke, siblings, daycare, insurance, and breastfeeding gave a 48% reduced chance of infant hospitalization among vaccinated mothers.

"Given that infants under 6 months of age have the highest hospitalization rate among all children and that the vaccine is not licensed for that age group, these data support that infants born to vaccinated mothers benefit from the transfer of maternally derived antibodies," write Poehling and colleagues in the American Journal of Obstetrics and Gynecology.

The team projects a yearly average of 19,130 influenza-attributable hospitalizations among infants under 6 months of age, therefore a reduction of 45-48% of these due to vaccination of mothers would result in an estimated 8600-9200 fewer per year, they conclude.

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Sarah Guy

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