Dealing with the Swine Flu Threat During Pregnancy

The worldwide death toll from swine flu is now at 700, according to the World Health Organization. And the U.S. government is gearing up for a mass vaccination campaign this fall, one not seen since the polio vaccine first became available in the 1950s. Earlier this week, the Food and Drug Administration approved the 2009-10 seasonal flu vaccine, but it doesn't include protection against the H1N1 strain that is responsible for swine flu. An H1N1 vaccine is still being tested for safety and efficacy. When it becomes available later this fall, should pregnant women be among the first to get it, or the last?

On the one hand, healthy pregnant women who get infected with the flu are at increased risk of serious illness and hospitalization. In fact, the second H1N1 flu death in the United States was a pregnant woman. Because of this greater risk, pregnant women are advised to get annual flu vaccinations. On the other hand, pregnant women also are advised to be very cautious when taking any medications—especially the newest ones—because of unknown health risks to the developing fetus. What's more, many folks remember the 1976 swine flu vaccination fiasco, when some 500 Americans out of the 43 million vaccinated developed a rare paralyzing condition called Guillain-Barré syndrome that may have been linked to the shot. Just today, public health experts said that there's no way to know if any rare side effects will occur in the new vaccine until millions of people are vaccinated. Those unknowns would make an expectant mom especially nervous.

There's also the question of thimerosal, a mercury-containing preservative that was banished from other childhood vaccines several years ago but is still used in most flu vaccines. In a previous blog post, I quoted thimerosal researcher Tom Burbacher, professor of environmental occupational health sciences at the University of Washington, saying that he thinks pregnant women should opt for a thimerosal-free flu vaccine. He's seen from his research on infant monkeys that the mercury in thimerosal passes into the brain and remains there for months. That's not to say that a single flu shot is unsafe, he says, but it's still best for pregnant women to minimize any exposure to mercury. The new H1N1 vaccine will come in a variety of formulations, including some that won't contain thimerosal, according to a spokesperson for the Centers for Disease Control and Prevention.

Pregnant women who want to avoid the compound, however, may need to search a bit to find a doctor who stocks thimerosal-free versions of both flu vaccines. Most gynecologists don't bother because the CDC doesn't say there's any need for pregnant women to avoid thimerosal. John Iskander, the previous head of immunization safety at the CDC, told me last fall that the reason the agency doesn't recommend thimerosal-free vaccines is because "there's still not enough women receiving the flu vaccine, and we don't want to throw up another barrier in the vaccination process." Most likely, the CDC will recommend that pregnant women get both vaccines this fall, but the agency hasn't yet finalized its recommendations for at-risk groups (including mothers-to-be).

In terms of other precautions pregnant women should take to minimize the risk of swine flu, the CDC advises pregnant women who have been exposed to someone infected with H1N1 to be treated with the antiviral drug Tamiflu. Ditto for those who have flu symptoms themselves. This advice—which doesn't apply to healthy women who aren't expecting—is due to the fact that H1N1 infections have led to more severe complications in pregnant women.

One piece of swine flu advice directed at British pregnant women, though, sounds pretty shocking to me. A few days ago the Department of Health in Britain began recommending that pregnant women stay indoors when possible and avoid taking public transportation to keep from getting infected with H1N1, according to the British Times Online. The agency also said expecting women should avoid crowds and should limit the movements of their kids so they don't bring the virus home. I'm guessing most pregnant women would ignore that advice—at least as long as the virus stays its course and doesn't become more dangerous.

Corrected on 07/24/09: An earlier version of this article misspelled Tom Burbacher's name.