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. 2018 May 3;36(19):2733-2739.
doi: 10.1016/j.vaccine.2017.08.080. Epub 2017 Sep 13.

Birth outcomes following immunization of pregnant women with pandemic H1N1 influenza vaccine 2009-2010

Abigail Eaton  1 , Ned Lewis  2 , Bruce Fireman  2 , John Hansen  2 , Roger Baxter  2 , Julianne Gee  3 , Nicola P Klein  2
Affiliations

Birth outcomes following immunization of pregnant women with pandemic H1N1 influenza vaccine 2009-2010

Abigail Eaton et al. Vaccine. .

Abstract

Background: Following the H1N1 influenza pandemic in 2009, pregnant women were recommended to receive both seasonal (TIV) and H1N1 influenza vaccines. This study presents incidence of adverse birth and pregnancy outcomes among a population of pregnant women immunized with TIV and H1N1 vaccines at Kaiser Permanente Northern California during 2009-2010.

Methods: We telephone surveyed pregnant Kaiser Permanente Northern California members to assess non-medically-attended reactions following H1N1, TIV or both vaccines during 2009-2010 (n=5365) in a separate study. Here we assessed preterm birth (<37weeks), very preterm birth (<32weeks), low birth weight (<2500 g, LBW), very low birth weight (<1500g), small for gestational age, spontaneous abortions, stillbirths and congenital anomalies among this cohort by comparing incidence and 95% confidence intervals between the following immunization groups: TIV only, H1N1 only, H1N1 prior to TIV immunization, TIV prior to H1N1 and both immunizations given at the same time.

Results: Results did not vary significantly between groups. Comparing H1N1 with TIV, incidence were similar for preterm births (6.37vs 6.28/100 births), very preterm births (5.30vs 8.29/1000 births), LBW (4.19vs 2.90/100 births), very LBW (4.54vs 5.52/1000 births), small for gestational age (9.99vs 9.24/1000 births), spontaneous abortion (7.10vs 6.83/1000 pregnancies), stillbirths (7.10vs 4.57/1000 pregnancies), and congenital anomalies (2.66vs 2.43/100 births).

Conclusions: Although constrained by small sample size, complex vaccine groups, and differential vaccine availability during 2009-2010, this study found no difference in adverse birth outcomes between H1N1 vaccine and TIV.

Keywords: H1N1; Influenza; Pregnancy; Safety; Vaccines.

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Figures

Fig. 1.
Fig. 1.
Original study population.
Fig. 2.
Fig. 2.
Incidence (with 95% confidence intervals) of preterm birth, low birth weight and congenital anomalies of babies born to mothers immunized by TIV only or any H1N1 among the study population of vaccinated pregnant women, October 2009–March 2010.
Fig. 3.
Fig. 3.
Incidence (with 95% confidence intervals of very preterm birth, very low birth weight, spontaneous abortion, stillbirth and small for gestational age following immunization by TIV only or any H1N1 among the study population of vaccinated pregnant women, October 2009–March 2010. * Incidence are per 100 births with the exception of spontaneous abortion and stillbirths, which are per 1000 pregnancies
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