Aug. 1 (UPI) -- A recent study from Ohio State University suggests that previous influenza vaccines can somewhat weaken the immune response in pregnant women, not baby.
The study, published Aug. 1 in Vaccine, included 141 pregnant women, 91 received a flu shot the previous year and 50 who did not receive a previous flu shot.
Researchers found that one month after receiving the flu vaccine, women with prior vaccination had higher baseline antibody concentrations and decreased antibody responses against all strains of influenza.
Those women also had lower antibody responses and seroconversion rates at one month post-vaccination compared to women who did not have a prior flu vaccine.
"The effect of lower antibody responses to flu vaccine among those with repeated vaccination has been shown in other studies, and the reasons for this are not well delineated," Lisa Christian, associate professor from the Institute for Behavioral Medicine Research at Ohio State University Wexner Medical Center, told UPI.
"Annual vaccination is still the best avenue for reducing the number of flu cases -- vaccination still provides protection, even if it is somewhat diminished among those with repeated vaccination."
Researchers found no significant differences in antibody concentrations or seroprotection rates in women or newborns at delivery, and no significant differences in efficiency of antibody transfer from mother to baby after testing umbilical cord blood.
Researchers say the results should not change the recommendations that annual flu vaccinations are the best way to protect against the flu. It is recommended that all women should get the flu vaccine during pregnancy due to their high risk of complications and to protect babies through the first six months of life before they are able to get their own flu vaccine.
"In addition, vaccination can reduce the severity of illness if it does occur," Christian said. "An important take away point from this study is that although women with prior vaccination exhibited lower antibody responses to current vaccination, this did not meaningful impact immunity conferred to the neonate."