The Safety of Influenza and Pertussis Vaccination in Pregnancy in a Cohort of Australian Mother-Infant Pairs, 2012–2015: The FluMum Study

Abstract

Background. Inactivated influenza vaccine (IIV) and pertussis vaccination are recommended in pregnancy. Limited safety data exist for women who received IIV vaccine during the first trimester of pregnancy or received both vaccines in pregnancy. We assessed adverse birth outcomes between vaccinated and unvaccinated pregnancies. Methods. Among prospectively enrolled Australian "FluMum" participants (2012-2015), primary exposure was receipt and timing of IIV during pregnancy. Primary outcomes included preterm birth, low birthweight at term (LBWT), and small for gestational age (SGA). We compared birth outcomes for IIV in pregnancy with women unvaccinated in pregnancy using Cox proportional hazard ratios (HRs) with 95% confidence intervals (CIs). Adjusted HRs (aHRs) controlled for potential confounding variables. Sensitivity analyses were conducted in a subgroup of women who received pertussis vaccination during pregnancy to assess whether associations between IIV and adverse outcomes were maintained after adjusting for pertussis vaccination. Results. Among 8827 participants in our study, women who received IIV in pregnancy did not have an elevated risk of an adverse birth outcome compared with unvaccinated pregnant women: preterm births (

Influenza vaccination in pregnancy among a group of remote dwelling Aboriginal and Torres Strait Islander mothers in the Northern Territory: The 1+1 Healthy Start to Life study

“…Data are lacking on the safety of vaccination in the first trimester of pregnancy, and on safety endpoints such as miscarriage, preterm births, stillbirths, LBW and SGA infants. One Australian study published in 2018 found no increased risk in preterm births, low birthweight or SGA infants in pregnant women who received a seasonal IIV compared to unvaccinated pregnant women, 39 however only 3% of this national cohort (N=8,827 mother-infant pairs) were Aboriginal women. Prior to 2015, analyses were largely limited to specific vaccines used during the influenza A(H1N1) pandemic, 40 and observational studies used in a meta-analysis 38 were non-Indigenous women living in well-resourced populations of North America and Europe.…”

Baseline incidence of adverse birth outcomes and infant influenza and pertussis hospitalisations prior to the introduction of influenza and pertussis vaccination in pregnancy: a data linkage study of 78 382 mother–infant pairs, Northern Territory, Australia, 1994–2015

“…It is unclear whether uptake is so poor due to the vaccine not being offered to pregnant women, vaccine refusal or failure to record vaccination receipt. There is recent evidence to suggest that the introduction of the maternal pertussis vaccination program has been the impetus for driving up IIV uptake in pregnancy since its implementation in 2015 [42] although the data are lacking for NT Aboriginal women and sample sizes for Aboriginal women in other states were small or absent [40, 43].…”

The Importance of Vaccinating Children and Pregnant Women against Influenza Virus Infection

“…Pregnant women are particularly susceptible to developing severe influenza illness and have an increased risk for hospital admission, although the mortality rate compared to non-pregnant women may not be increased [156][157][158]. Overall, it has been established that vaccinating pregnant women is safe, with no evidence demonstrating a link between immunization during pregnancy and adverse outcomes in offspring [159][160][161][162][163][164][165]. Infants born to mothers who were vaccinated against influenza may have a decreased rate of preterm birth, low birthweight, and stillborn birth, although establishing a causal relationship is challenging [160,[166][167][168][169][170][171].…”

“…Such data are valuable, however, a deeper understanding of additional factors that could have contributed to an adverse event is necessary in order to minimize the risk of drawing an invalid conclusion associating an adverse event with vaccination. Vaccinating pregnant women is generally regarded as safe [159][160][161][162][163][164][165]. However, some hesitancy over influenza vaccination is present in this population and the benefit of protecting both the mother and the fetus needs to be conveyed as outweighing the risk of potential side effects [223][224][225][226].…”