The flu shot is safe for pregnant women, does not increase the risk of spontaneous abortion
Studies have shown that the inactivated flu vaccine is safe for pregnant women and their unborn children. It also reduces the likelihood of influenza-related complications during pregnancy for both mothers and their infants.
Misrepresents a complex reality: The study cited to support this claim does not account for potential risk factors which may contribute to spontaneous abortion, nor does it compare its findings to the baseline risk for spontaneous abortion in unvaccinated women.
Misleading: The U.S. Vaccine Adverse Events Reporting System (VAERS) provides data on adverse events which occur after vaccination, but does not establish whether those events were caused by the vaccines.
The article containing this claim was published in November 2012, but went viral on Facebook in late 2019. It claims that there was a “4,250% increase in fetal deaths reported to VAERS after flu shot given to pregnant women” and concludes that the flu shot “was causing a massive spike in fetal deaths”.
The article bases its claim in part on a 2012 study which reported that the number of fetal losses recorded in the U.S. Vaccine Adverse Events Reporting System (VAERS), increased from 4 during the single-vaccine 2008/2009 season to 174 during the two-vaccine 2009/2010 season. The study’s author attributes this to a “toxicity effect” from the double dose of the flu vaccine that pregnant women received during the 2009/2010 season.
The increase in the number of fetal losses between the two seasons was indeed 4,250%, but these losses occurred in different sized population groups. Therefore, this number does not reflect an increase in the rate of fetal loss. In addition, the study contains several major flaws. Firstly, the VAERS data used in the study include all adverse events that follow vaccination whether they were proven to have been caused by the vaccine or not. Adverse events can be reported by anyone, including healthcare providers, patients, or family members, and as VAERS states, “no proof that the event was caused by the vaccine is required in order for VAERS to accept the [adverse event] report.”
Secondly, Goldman did not examine whether the vaccinated women were at risk for spontaneous abortion due to other factors, such as advanced maternal age, smoking, or alcohol use, which may have contributed to the increase in fetal losses between the two seasons.
Thirdly, spontaneous abortions also occur in unvaccinated pregnant women, but Goldman did not compare the rates of spontaneous abortion between unvaccinated and vaccinated populations. Therefore, the study does not show that the flu vaccine causes an increased risk of fetal loss because it did not investigate whether the risk associated with vaccination is actually higher than the baseline rate.
In short, the study’s author mistakenly concluded that the fetal losses must be the result of the flu shot simply because they occurred at some point after vaccination (this is known as the post hoc ergo propter hoc fallacy).
Numerous studies, as well as the American College of Obstetrics and Gynecology, have reported that the inactivated flu vaccine is safe for pregnant women and unborn children[2,3,4], and that thimerosal used in the flu vaccine is not a cause for concern. Furthermore, by reducing the risk of influenza infection, the flu shot may actually prevent congenital abnormalities associated with maternal respiratory infection, as shown by a review and meta-analysis of more than 20 studies. Infants born to women who are severely ill with influenza are also more likely to have poorer outcomes, such as low birth weight and Apgar scores[6,7,8,9].
- 1 – Goldman G. (2012) Comparison of VAERS fetal-loss reports during three consecutive influenza seasons: Was there a synergistic fetal toxicity associated with the two-vaccine 2009/2010 season? Human and Experimental Toxicology.
- 2 – Moro et al. (2011) Adverse events following administration to pregnant women of influenza A (H1N1) 2009 monovalent vaccine reported to the Vaccine Adverse Event Reporting System. American Journal of Obstetrics and Gynecology.
- 3 – Fell et al. (2015) Fetal death and preterm birth associated with maternal influenza vaccination: systematic review. British Journal of Gynaecology.
- 4 – Zerbo et al. (2017) No association between influenza vaccination during pregnancy and adverse birth outcomes. Vaccine.
- 5 – Luteijn et al. (2014) Influenza and congenital anomalies: a systematic review and meta-analysis. Human Reproduction.
- 6 – Newsome et al. (2019) Outcomes of infants born to women with influenza A(H1N1)pdm09. Birth Defects Research.
- 7 – Richards et al. (2013) Neonatal outcomes after antenatal influenza immunization during the 2009 H1N1 influenza pandemic: impact on preterm birth, birth weight, and small for gestational age birth. Clinical Infectious Diseases.
- 8 – Naresh et al. (2013) A multicenter cohort study of pregnancy outcomes among women with laboratory-confirmed H1N1 influenza. Journal of Perinatology.
- 9 – Vazquez-Benitez et al. (2016) Risk of Preterm or Small-for-Gestational-Age Birth After Influenza Vaccination During Pregnancy: Caveats When Conducting Retrospective Observational Studies. American Journal of Epidemiology.