Flu vaccine in pregnancy protects infants

Babies born to mothers who received flu shots while pregnant were less likely to have lab-confirmed flu by six months of age, a finding doctors say strengthens calls to immunize pregnant women.

Flu is associated with increased rates of hospital admission because of respiratory illness among pregnant women and a burden on the health of newborns. Currently,guidelines in Canadaand the U.S. recommend immunizing pregnant women with seasonal flu vaccines given the benefits to mom and the antibody protection it offers to the infant.

In Tuesday's issue of the journal Pediatrics, researchers at the University of Utah checked hospital records for more than 245,000 pregnant women and 249,000 babies in Utah and Idaho for flu seasons between 2005 and 2014 to compare how well the babies fared from flu.

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Among 658 infants with laboratory-confirmed influenza, 638 cases (2.83 per 1,000) were born to women who were not immunized. In comparison, 20 (0.84 per 1,000) were born to women who said they had a flu shot, the researchers said.

In total, 151 infants with flu were hospitalized, three in the immunized mothers group and 148 among those born to unimmunized mothers.

'Public health priority'

"Protecting young infants from influenza through maternal immunization during pregnancy is a public health priority," assistant pediatrics Prof. Julie Shakib from the University of Utah and her colleagues concluded.

During pregnancy,Shakib said, women experience changes in their heart, lungsand immune system that make them more susceptible to severe illness from flu and increase their risk of premature labour.

To improve vaccine uptake,Shakib suggested that all obstetric providers should recommend the influenza vaccine to all pregnant women and be able to provide it.

To check if the immunized benefits weren't just related to chance, the researchers also looked at the incidence of respiratory syncytial virus or RSV, a respiratory infection that also occurs in infants and young children during the winter.

They found no differences in RSV infection in infants born to women who had a flu shot, which they said increases confidence that that giving a flu vaccine during pregnancy results in benefits to the baby specific to the flu.

Vaccination rates need to be higher, doctor says

About 10 per cent of the women reported being vaccinated while pregnant.

Dr. Noni MacDonald, a professor of pediatrics at Dalhousie University and the IWK Health Centre in Halifax, found similar benefits for newborns in a 2014 study published in the Canadian Medical Association Journal. Infants also showed benefits when their mothers were immunized against flu in a randomized trial in Bangladesh.

"The disquieting part of our study and the one reported in Pediatrics is that the rates of influenza immunization in pregnancy are far lower than needed to optimize outcomes for infants," MacDonald said in an email.

"Uptake of this vaccine, as it is both safe and effective in helping to protect the mother and the infant against influenza, must beimproved to maximize outcomes for both. Influenza infection can be a very serious, even life-threatening in both pregnant women and in their offspring in the first six months of life prevention is key to decreasing the risks."

The U.S. researchers encouraged pregnant women to ask for a flu shot if their caregivers don't offer it.

The study was funded by the U.S. National Institutes of Health.