A new study confirms that giving H1N1 flu vaccines to pregnant women during the 2009 swine flu pandemic was safe for them and their babies, and likely reduced the risk of miscarriage and stillbirth.
Norwegian researchers launched the study because of concerns over the safety of vaccines, especially the new vaccine to combat pandemic flu. Thirty women in Norway reported miscarriages after receiving the H1N1 shot, according to the study, published today in The New England Journal of Medicine.
Those fears weren’t borne out by the data, however, when researchers looked at the larger picture: 117,347 pregnancies in Norway from 2009 through 2010. More than half of all pregnant women in Norway received the H1N1 shot — a fact that doctors can accurately calculate because of that country’s national health system.
In fact, the vaccines offered substantial benefits, says co-author Camilla Stoltenberg, from the Norwegian Institute of Public Health.
Vaccinated pregnant women were 70% less likely to develop H1N1 flu than unvaccinated women, the study says.
Developing H1N1 flu was extremely dangerous: Pregnant women who contracted the flu were nearly twice as likely to experience miscarriage or stillbirth, the study says.
Unvaccinated women were 25% more likely to miscarry or have a stillbirth, although this finding could have been due to chance, due to the relatively low rate of fetal death. There were about five miscarriages or stillbirths for every 1,000 live births in Norway during this period.
The findings, which are supported by previous research demonstrating the safety of flu vaccines during pregnancy, come at an opportune time, amid an early and severe flu season, says Siobhan Dolan, an obstetrician-gynecologist at Montefiore Medical Center in New York and a medical adviser to the March of Dimes.
“There has been this misconception that getting a flu shot, or a vaccine in general, is risky during pregnancy,” Dolan says. “But it’s the flu that poses the greatest risk, not the shot,” says Dolan, who was not involved in the new study.
The Centers for Disease Control and Prevention recommends an annual flu shot for everyone over 6 months old, including pregnant women.
Women can be vaccinated safely any time during pregnancy, Dolan says.
Studies also show that getting vaccinated against flu during pregnancy protects the baby for the first few months of life, when it is too young to be vaccinated, Stoltenberg says. Newborns are especially vulnerable to complications from influenza, because of their immature immune systems and small airways.
The Norwegian study — supported by the Norwegian Institute of Public Health and the U.S. National Institutes of Health — involved a slightly different H1N1 vaccine from that used in the USA, says Gregory Poland, a professor and vaccine researcher at the Mayo Clinic in Minnesota. Norwegians added an adjuvant to their vaccine, which is intended to produce a stronger immune response.
H1N1 flu vaccines in the USA did not contain adjuvants, due to concerns by some consumers about their safety, says Poland, who was not involved in the new study.
Pregnant women face increased risks from the flu for many reasons, Dolan says. Their immune systems are weaker than usual, and their lung capacity is less, for example.
The greatest risk from a flu vaccine is Guillain-Barre syndrome, Poland notes, which may occur in an additional one in every 1 million people if they get the vaccine.
Guillain-Barre is a condition in which the body’s immune systems attack its nerves, often after infection with a respiratory bug or stomach flu. Although acute cases are an emergency, most people recover completely, according to the Mayo Clinic.
Poland notes that anecdotes about adverse reactions from vaccines can be misleading. When women miscarry after getting a vaccine, it’s most likely a coincidence, although it may not feel that way to a woman who has just lost a pregnancy.
“Thousands of miscarriages are going to occur within a week of when we give influenza vaccines, but that is a coincidence,” Poland says.
What consumers don’t see, he says, are the ravages of influenza that doctors treat every day.
“We plead with patients to get the vaccine, because we see what is going to happen,” Poland says. “In our hospital right now, we have 80 people critically ill from the flu in the hospital and intensive-care unit.”
Poland adds, “The risks from influenza vaccine are so small that they can’t be reliably measured. The risks of flu to mother and baby are very real.”
Courtesy of USA Today