Flu Vaccine Benefits Pregnant Mothers & Their Unborn Babies

by Amy Spangler
June 05, 2012

Fears over vaccine safety cause many individuals, particularly pregnant women, to forgo the seasonal flu vaccine and take a “wait and see” approach.

Prior to the 2009–2010 H1N1 pandemic, vaccination rates among pregnant women in the U.S. ranged from 0.7 percent to 20 percent. During the pandemic, an intensive vaccination campaign prompted a greater number of pregnant women to get the vaccine, allowing researchers to better assess the effect of the vaccine on pregnant women and their unborn babies.

A recent report published in the June issue of the American Journal of Public Health, chronicled the health outcomes of a group of pregnant women who gave birth between November 2, 2009 and April 30, 2010 during the H1N1 pandemic.

Research
Researchers assessed the medical records of 55,570 women—42 percent chose to receive the H1N1 vaccine during pregnancy, either alone (91.5 percent) or in combination with the seasonal flu vaccine (8.5 percent) and 58 percent declined to be vaccinated. The researchers tallied: the number of very preterm births (VPB)—babies born at less than 32 weeks gestation; small for gestational age (SGA) babies—babies with birth weights well below normal based on their age; babies with 5-minute Apgar scores below 7—Apgar scores range from 0-10 and are a composite of five measure of infant health; and stillborn babies—babies who die while still inside the uterus.

Results
Pregnant women who became infected with H1N1 during the pandemic were more likely to be hospitalized than non-pregnant flu patients. This finding supports the theory that pregnant women infected with the seasonal flu are more likely than non-pregnant women to experience serious illness and therefore benefit most from the flu vaccine.

After adjusting for maternal age, history of preterm birth, smoking, high blood pressure, education, and family income, researchers also found that women receiving the H1N1 vaccine had a significantly lower risk of VPB (27 percent)—a predictable finding given that maternal infection is a known risk factor for preterm birth. Additionally, women who received the H1N1 vaccine were less likely to deliver a SGA baby (19 percent) and less likely to experience a stillbirth (34 percent) compared to women who chose to forgo the vaccine. There was no difference in 5-minute Apgar scores between babies born to vaccinated women and those born to women who were not vaccinated.

Recommendations
The Centers for Disease Control and Prevention (CDC) currently recommend that all pregnant women receive the seasonal flu vaccine. “Getting a flu shot is the first and most important step in protecting against flu. The flu shot given during pregnancy has been shown to protect both the mother and her baby (up to 6 months old) from flu,” says the CDC. Pregnant women are urged to get a flu shot and avoid the nasal spray. The shot contains inactivated (dead) virus while the nasal spray contains live virus.

Despite the effectiveness of the H1N1 vaccine, there is no guarantee that future flu vaccines will work as well. Each year there are new types and strains of flu viruses. Scientists estimate which viruses will circulate in any given year and produce vaccine based on their predictions. In 2009–2010, there was a precise match between the circulating viruses and the vaccine. But according to the CDC, even if the vaccine is “less than an ideal match” it can still protect against other viruses.