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16-02-2012 | Gynaecology | Article

Maternal influenza vaccination benefits mothers and babies

Abstract

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MedWire News: Maternal influenza immunization during pregnancy is associated with better neonatal outcomes, a post hoc analysis of trial data suggests.

In the cohort of pregnant Bangladeshi women, those who were immunized during the influenza season were less likely to have babies that were small for gestational age or of low birthweight, than nonimmunized women.

The finding comes from a secondary analysis of data from the Mother'sGift project, a randomized trial designed to test the safety and efficacy of inactivated influenza and pneumococcal vaccines during pregnancy.

Over an 18-month period, 340 pregnant women in Bangladesh received either inactivated influenza vaccine or 23-valent pneumococcal polysaccharide vaccine (control).

Neonatal outcomes were assessed following maternal influenza immunization in two time periods: when influenza virus was not circulating (September 2004 through January 2005), and when influenza virus was circulating (February through October 2005).

When there was no circulating influenza virus, neither maternal nor neonatal outcomes differed between the treatment groups, the researchers report.

When an influenza virus was circulating, however, a range of outcomes were significantly better in women who had received the influenza vaccine than controls.

Specifically, the incidence of respiratory illness with fever was significantly lower for both mothers and infants who had received the influenza vaccine than in those who had received control, at 3.7 versus 7.2 per 100 person-months.

Also during this period, the proportion of babies who were small for gestational age was lower in the influenza vaccine group than in the control group (25.9 vs 44.8%), while mean birthweight was higher among infants whose mothers received the influenza vaccine than among those who received the control vaccine (3178 vs 2978 g).

"Our data suggest that the prevention of infection with seasonal influenza in pregnant women by vaccination can influence fetal growth," write Mark Steinhoff (Cincinnati Children's Hospital, Ohio, USA) and co-authors in the Canadian Medical Association Journal.

The researchers calculate that 10 maternal influenza vaccinations given year-round would prevent one small-for-gestational-age birth, dropping to six vaccinations during the period in which the influenza virus was circulating.

They conclude: "If our data about the effect of antenatal influenza immunization on fetal development are confirmed, the existence of effective antenatal immunization delivery systems suggests influenza vaccine may be a feasible addition to routine antenatal immunization programs."

By Joanna Lyford

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