Medical Professional Publications

Babies Benefit From Maternal Influenza Vaccine – Even if Mother Has a Diminished Immune Response

(From the September 2017 issue of Research Now)

Repeated flu shots weaken pregnant women’s initial immune response, but still protect newborns. 

Influenza vaccination is recommended annually to everyone 6 months of age and older, including pregnant women. Pregnant women and newborns are both at risk for complications, hospitalizations, and even death from the flu. Flu shots during pregnancy protect both mothers and babies who are too young to receive vaccinations themselves. 

However, repeated vaccination can dampen antibody responses: those who receive a flu shot one year have lower antibody responses in the following year. 

What might repeated vaccination mean for pregnant women and their babies? To answer this question, researchers from Nationwide Children’s Hospital and The Ohio State University collaborated on a study to examine the effects of prior vaccination on antibody responses to seasonal flu vaccine in pregnant women and their newborns. 

The researchers measured influenza antibody levels in women pregnant women prior to receiving the vaccine, 30 days post-vaccination, and at delivery. At that time, they also tested umbilical cord blood to see how well the mothers’ vaccinations conferred protection to their babies. 

Women who had not received a flu shot in the previous year had better initial immune responses to the vaccine. In those who had received a prior flu shot, their peak antibody responses were weakened. However, prior maternal vaccination did not affect antibody levels transferred to newborns.

“Even though the maternal antibody responses were dampened in the women who had been vaccinated the previous year, antibody transfer to the newborns was not meaningfully affected by prior vaccination of the mother,” says Lisa Christian, PhD, a psychologist at The Ohio State University Wexner Medical Center and lead author of the study. 

Octavio Ramilo, MD, chief of infectious diseases at Nationwide Children’s and co-author of the study, says this is good news.

“Even if a woman gets vaccinated every year, receiving a vaccine while pregnant still provides a significant benefit for the baby,” says Dr. Ramilo, who is also a professor of pediatrics at the Ohio State University College of Medicine.

“This study is important because it demonstrates that the recommendations we have – that all of us, including pregnant women, should get vaccinated every year for the flu – are the best protection for mothers and babies,” says Dr. Ramilo. 

Dr. Christian agrees.

“These results provide reassurance that even though the dampening of antibody responses in the mother may occur in women with repeated vaccination, the protection conferred to the newborn should be equivalent,” she says. “The best policy is for everyone to get vaccinated because the protection from vaccines comes from the overall population being protected.”

Drs. Christian and Ramilo are continuing to examine different factors that could affect the vaccine response in pregnant women and their babies. Next, they will look at the extent to which psychosocial factors, such as depression, stress, and obesity, modify the antibody responses in pregnant women and antibody transfer to newborns. A more nuanced understanding of the vaccine response across individuals might help researchers identify ways to improve the vaccine. 

Reference:

Christian, L. M., Beverly, C., Mitchell, A. M., Karlsson, E., Porter, K., Schultz-Cherry, S., and Ramilo, O. (2017). Effects of prior influenza virus vaccination on maternal antibody responses: Implications for achieving protection in the newborns. Vaccine. doi: 10.1016/j.vaccine.2017.05.050.

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