Newborn Has Flu Protection from Mom’s Shot

When expectant mothers get a flu vaccination, they may help safeguard their babies against flu for the first few months of life.

A study published in the Archives of Pediatrics & Adolescent Medicine found that when women were vaccinated in the second or third trimester of pregnancy, their babies were significantly less likely to get the flu.

The researchers found that babies' blood showed evidence of antibodies to the flu.

“Infants younger than 6 months are more likely to be seriously ill or to die from flu infections than older children," says Kevin Lorah, MD, Medical Director for Children's Services at Lancaster General Health, and Medical Director of the NICU at Women & Babies Hospital.

"However, the influenza vaccine is not approved for children younger than 6 months of age," Dr. Lorah adds. "This makes this immunization particularly significant for pregnant women.”

Protecting the Youngest from the Flu

"Influenza infection among young infants can be a serious illness," says study author Katherine O'Brien, M.D., at Johns Hopkins Bloomberg School of Public Health.

"There are several ways of protecting young infants against influenza," says Dr. O'Brien. "One is to assure that those in contact with young infants are immunized for influenza.

“Other ways are to practice good hygiene and hand washing, as well as keeping infants away from people who are known to be ill,” she says. “And, this study shows if the pregnant mother is immunized during pregnancy, it affords protection to the infant.”

Infants younger than 6 months are more likely to be seriously ill or to die from flu infections than older children. However, the influenza vaccine is not approved for children younger than 6 months of age.

Young babies may acquire antibodies against some strains of influenza from their mother's blood, but this immunity may not match the currently circulating strains of flu often covered in the current year's vaccine.

To assess whether a vaccine given to the mother would provide any immunity to her offspring, the researchers followed 1,160 mothers who gave birth during one of three influenza seasons.

All of the mothers lived on either the Navajo or White Mountain Apache Indian reservation. Dr. O'Brien says people living in these areas have a higher risk of respiratory illness during influenza season than residents of other areas of the country.

During the study, 49 percent of the women chose to get the influenza vaccine during the second or third trimester of pregnancy.

The researchers found a 41 percent reduction in the risk for lab-confirmed flu infection in babies whose mothers received the influenza vaccine. Babies born to mothers who received the flu immunization also had a 39 percent decreased risk of being hospitalized because of the flu.

When the researchers tested blood samples from the infants, they found that babies whose moms had been vaccinated had higher levels of antibodies against the strains of flu included in the vaccines than babies whose mothers chose not to be immunized.

Keeping women and babies healthy

Dr. O'Brien says she believes these findings can be generalized to other groups.

"There's no reason to believe this wouldn't be an important strategy for protecting all infants," she says.

Kathleen Neuzil, M.D., M.P.H., agrees. "We already know that pregnant women are at a higher risk of morbidity from influenza,” she says. “And we already know we should be vaccinating just to prevent the disease in pregnant women, but this study gives us just another reason, and another positive reason, to encourage influenza vaccinations."

Dr. Neuzil is director of the influenza vaccine program at PATH, a global nonprofit health organization, and co-author of an accompanying editorial in the same issue of the Archives of Pediatrics & Adolescent Medicine.

"Pregnant women should get the influenza vaccine, and if they don't want to do it for themselves, here's a reason - you can protect your unborn baby as well," she says.

Always talk with your doctor to find out more information.