Infants have a much lower risk of getting influenza when their mothers are vaccinated against the virus during pregnancy, a U.S. study confirms.

"Babies cannot be immunised during their first six months, so they must rely on others for protection from the flu during that time," said the study’s lead author, Dr. Julie Shakib.

Babies 6 months and younger whose mothers had a flu vaccine during pregnancy were 70 percent less likely to have lab-confirmed flu than babies born to mothers who didn’t have the immunization while pregnant. In addition, the babies born to mothers immunized during pregnancy had an 80 percent reduction in flu-related hospitalizations, the study found.

"When pregnant women get the flu vaccine there are clear benefits for their infants." For the study, the researchers reviewed more than 245,000 health records of pregnant women and more than 249,000 infant records. Information was available for nine flu seasons from December 2005 through March 2014.

Only about 10 percent of these women reported being vaccinated while pregnant, the study revealed.

A total of 151 of the 658 infants were hospitalised, with 148 being born to non-immunised pregnant women.

The flu risk begins even before women leave the hospital after delivery. Shakib said-"We just really hope more pregnant women get the vaccine" .

"That's the take-home message of the study."