Is the Flu Shot Safe During Pregnancy?
Pregnancy during flu season can be particularly dangerous.
A pregnant woman’s heart and lungs are already doing extra work handling the pregnancy, so a serious illness like the flu can put her in danger of complications like pneumonia. The flu has also been linked in previous studies with preterm labor and premature birth; and fever from the flu can lead to birth defects. The flu shot has been given to millions of pregnant women over many years. Flu shots have never been shown to cause harm to pregnant women or their babies, but pregnant women have been shown to be at increased risk for morbidity and death from flu.
Pregnancy is a dangerous time for women. Your fetus is comprised of your own, plus “foreign” non-self DNA. Normally, your immune system will do anything it can to kill off a foreign invader. But, you don’t want to mount an immune response against your baby during pregnancy. In fact, your immune response will be repressed, so that you can successfully carry your fetus to term. Pretty neat. except….. during flu season.
A recent study analyzed 58,008 births in Western Australia between April 2012 and December 2013. Among the women, 8.8 percent had received the flu vaccine, and 377 stillbirths occurred at a rate of 5.0 per 100,000 pregnancy days for women without the vaccine and 3.0 per 100,000 days for women who received the vaccine.
Overall, stillbirth was 51 percent less likely among vaccinated mothers, as opposed to unvaccinated mothers, with the largest reduction in stillbirths coming just after flu season ended. Maternal vaccination against flu was recommended as far back as 1960 in the US and in 2005 by the World Health Organization (WHO). In England, it was first recommended for pregnant women during the swine flu pandemic of 2009.
It is safe, and very important, for a woman who is pregnant to receive a flu vaccine. Pregnant women who get the flu are at increased risk for severe illnesses from influenza and their babies are also at risk. Complications from the flu can include premature labor, babies that are small for gestational age, hospitalization, and, death. Pregnant women can receive the flu shot at any time, during any trimester. In addition, because babies younger than 6 months are too young to receive flu vaccine, it is important that everyone who cares for your baby also get a flu vaccine.
Influenza is the most frequent cause of death from a vaccine-preventable disease in the United States. In a study of influenza seasons from 1976–1977 through 2006–2007, the estimated number of annual influenza-associated deaths from respiratory and circulatory causes ranged from a low of 3,349 (1985–1986 season) to a high of 48,614 (2003–2004 season), with an average of 23,607 influenza-associated deaths. In addition to fatalities, seasonal influenza is also responsible for more than 200,000 hospitalizations per year.
No study to date has demonstrated an increased risk of either maternal complications or adverse fetal outcomes associated with inactivated influenza vaccination. Moreover, no scientific evidence exists that thimerosal-containing vaccines are a cause of adverse events among children born to women who received influenza vaccine during pregnancy.
“Inactivated influenza vaccine reduced proven influenza illness by 63% in infants up to 6 months of age and averted approximately a third of all febrile respiratory illnesses in mothers and young infants. Maternal influenza immunization is a strategy with substantial benefits for both mothers and infants. (ClinicalTrials.gov number, NCT00142389.)”
“Inactivated influenza vaccine can be safely and effectively administered during any trimester of pregnancy. No study to date has demonstrated an increased risk of either maternal complications or adverse fetal outcomes associated with inactivated influenza vaccination. Moreover, no scientific evidence exists that thimerosal-containing vaccines are a cause of adverse events among children born to women who received influenza vaccine during pregnancy.”
“Infants born to women reporting influenza immunization during pregnancy had risk reductions of 64% for ILI, 70% for laboratory-confirmed influenza, and 81% for influenza hospitalizations in their first 6 months. Maternal influenza immunization during pregnancy is a public health priority.”
Effects of influenza on pregnant women and infants. Rasmussen SA1, Jamieson DJ, Uyeki TM.Am J Obstet Gynecol. 2012 Sep;207(3 Suppl):S3–8. doi: 10.1016/j.ajog.2012.06.068. Epub 2012 Jul 9.
Seasonal Trivalent Influenza Vaccination During Pregnancy and the Incidence of Stillbirth: Population-Based Retrospective Cohort Study. Annette K. Regan, Hannah C. Moore, Nicholas de Klerk, Saad B. Omer, Geoffrey Shellam, Donna B. Mak, and Paul V. Effler
Safety of influenza vaccination during pregnancy. Am J Obstet Gynecol. 2009 Dec;201(6):547–52. doi: 10.1016/j.ajog.2009.09.034. Epub 2009 Oct 21. Tamma PD1, Ault KA, del Rio C, Steinhoff MC, Halsey NA, Omer SB.