Influenza vaccination during pregnancy safe in terms of maternal gestation age, infant birthweight
Obtaining an influenza vaccination during pregnancy does not impact infant birthweight or gestation age at birth, a study from Australia found.
There was no significant difference in birthweight between infants born to vaccinated (3,337 g) and unvaccinated women (3,352 g; p=0.29). There was also no significant difference in infant birthweight between mothers who received the vaccine during the first, second, or third trimester of pregnancy compared with unvaccinated mothers. [Vaccine 2017;doi:10.1016/j.vaccine.2017.01.075]
The overall mean gestational age at birth was 38.7 weeks and did not differ between vaccinated (38.7 weeks) and unvaccinated women (38.8 weeks; p=0.051).
“The results arising from this study are reassuring in relation to the safety of receiving influenza vaccination during any stage of pregnancy, with respect to gestational age at birth and infant birthweight,” said the researchers.
Subjects in this nested, retrospective cohort study were 7,126 mother-infant pairs (mean maternal age at infant birth, 31.7 years, influenza vaccine uptake in pregnancy, 34 percent) recruited for the FluMum* study between April 2012 and December 2014. Of the 2,399 women who received an influenza vaccination while pregnant (1,705 with known vaccination date), 51 percent (n=863) received the vaccine during the second trimester. Eighty-three percent of the infants were born during the Australia influenza season (March–September).
In a univariate analysis, pregnant women with any pre-existing comorbidities or influenza risk factors were more likely to receive an influenza vaccination during pregnancy compared with women with no comorbidities or risk factors (RR, 1.13, 95 percent CI, 1.04–1.24; p=0.007), though the risk difference was a modest 2.8 percent.
“Maternal influenza vaccination is a public health policy initiative that has been advocated for more than a decade in Australia without any systemic initiatives to monitor implementation, effectiveness, or safety,” said the researchers.
“Providing further evidence around the safety of receiving a vaccine during any trimester of pregnancy, particularly outcomes for infants, may help reassure pregnant women and healthcare providers and thereby help increase uptake of the vaccine,” they said, an action that they hope will reduce the mortality and morbidity associated with an influenza infection during pregnancy. They also encouraged further research into other birth outcomes after vaccination during pregnancy.