By Ed Susman
PHILADELPHIA -- October 30, 2009 -- Vaccinating pregnant women against influenza virus results in a lower risk of having a premature or low birth-weight baby, researchers stated here at the 47th Annual Meeting of the Infectious Diseases Society of America (IDSA).
However, even during influenza season few pregnant women receive the vaccinations.
Unvaccinated mothers were 56% more likely to have a premature baby (born <37 weeks gestation) than women who had been vaccinated (P = .001), according to Saad B. Omer, PhD, Global Health, Emory University, Atlanta, Georgia.
"We found an association between maternal influenza immunisation and reduced rates of prematurity during any influenza activity period," said Dr. Omer on October 29.
Dr. Omer and colleagues analysed data from the Georgia Pregnancy Risk Assessment Monitoring System (PRAMS) to evaluate the association between maternal influenza immunisation and prematurity and birth weight-related outcomes. The team scrutinised outcomes involving 6,410 births between June 2004 and September 2006.
He said that just 15% of women in the cohort had received vaccinations against influenza.
"During the period of widespread influenza activity in rates of small for gestational age infants were decreased among women who were vaccination," Dr. Omer said. He added that women who did get vaccinated had a 72% reduced risk of having a child that was small for gestational age (P = .01).
However, Dr. Omer said that when births occurred outside of influenza season, there did not appear to be an effect on prematurity or on birth weight. Although the findings need to be replicated, he said, "influenza vaccination may be an important tool for addressing the problem of immaturity."
The findings might help bring the question of vaccination to the attention of obstetricians, who tend not to consider vaccinations with their patients, said William Schaffner, MD, Preventive Medicine, Vanderbilt University Medical Center, Nashville, Tennessee. Dr. Schaffner moderated a press briefing at which the findings by Dr. Omer were presented.
"This is powerful information for obstetricians and pregnant women to have," said Dr. Schaffner.
"There is a need for expanding efforts for improving maternal influenza immunisation rates," Dr. Omer said.
[Presentation title: Impact of Maternal Immunization Against Influenza on Prematurity and Birth Weight. Abstract 703]
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