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Anthrax Vaccine Found Safe for Women, Babies

Study of female recruits finds shot won't harm fertility or fetus

TUESDAY, March 26, 2002 (HealthDayNews) -- The anthrax vaccine won't harm either a woman's fertility or her baby -- even if she gets pregnant shortly after being vaccinated.

That's the word from a new study of more than 4,000 female U.S. Army recruits appearing in tomorrow's Journal of the American Medical Association. The study, said to be the first to examine the effects of the anthrax vaccine on reproduction in a large number of women, offers encouraging news in the event that a nationwide anthrax vaccine program goes into effect.

"This study found no association between fertility [likelihood of becoming pregnant] and anthrax vaccination. Further, once pregnant, there was no difference in birth rates or adverse birth outcomes," says Dr. Andrew Wiesen, chief of epidemiology and disease control at Madigan Army Medical Center in Tacoma, Wash., and the study's lead author.

"This should be interpreted as comforting news to women who might need to receive the vaccine, in that there is no evidence the vaccine will affect future fertility," he adds.

For those not involved in the study, including chemical weapons expert Philip Tierno, the finding is not shocking. Still, he says, it is reassuring.

"The anthrax vaccine is believed to be one of the safest vaccines around today, so it does not surprise me that it had no effect on fertility or on the children that were born to vaccinated mothers," says Tierno, who is the director of clinical microbiology at the New York University and Mount Sinai Schools of Medicine and a member of the New York City Mayor's Task Force on Bioterrorism.

"I do, however, think it's important that this study was done now, so that in the event that a woman does need to get a vaccine, she does not have to fear harming her chances of getting pregnant or any baby she might conceive after being vaccinated," Tierno adds.

According to Wiesen, the anthrax vaccine is the acellular type -- meaning it contains only the protein portion of the bacteria. The main immunizing component in the vaccine, Wiesen says, is called a protective antigen, and it alone cannot cause anthrax. It does, however, stimulate the body to produce antibodies to the antigen.

"If the body was exposed to the anthrax toxin in the future, the antibodies to protective antigen would inactivate/destroy the toxin before it could harm the body," says Wiesen.

Wiesen, a U.S. Army major, led the study in his previous position as a chief of preventive medicine at Winn Army Community Hospital in Ft. Stewart, Ga. It involved 4,092 women between the ages of 17 and 44, all members of the U.S. Army stationed at one of two Georgia camps from January 1999 to March 2000.

Of the group, 3,136 received at least one dose of the anthrax vaccine; most received two to three doses. Ideally, the vaccine is administered in six doses over 18 months.

Within the 15-month study, 513 women became pregnant, 385 of whom had received at least one dose of the vaccine.

After adjusting for factors that could influence the findings, including age, race and marital status, researchers found that pregnancy rates were nearly identical in those who had the vaccine and those who did not.

Because many of the women were transferred before the study was completed, follow-up was possible on just 488 of the new mothers. Of that group, the rate of adverse birth outcomes -- including birth defects -- appeared to be virtually equal in both groups as well.

However, because the overall rate of defects was so small, the authors report that the study "did not have adequate statistical power" to rule out a possible small effect of vaccination on birth outcomes.

While the news is good, the authors themselves offer an important caveat: While most of the women in the study had up to four shots of the six-dose vaccine before getting pregnant, none had the full complement of shots -- either because they were transferred or because they became pregnant and stopped taking the vaccine. As such, the study did not allow for a complete-dose response analysis -- meaning there is no proof that the study outcome would have been different had the women received all six doses.

However, Wiesen says he is confident that, according to information gleaned from the study, the response at six doses would be similar to what was found with one dose or two or three doses -- particularly since the overall lack of any effect was so pronounced.

The anthrax vaccine was licensed by the U.S. Food and Drug Administration for use in humans in 1970. Before 1990, use was limited to those at highest risk, including certain veterinarians and laboratory workers. Since 1998, the U.S. military has given more than two million doses of the vaccine to more than 500,000 men and women without major ill effects.

Earlier this month, the Institute of Medicine concluded that the anthrax vaccine was safe and effective, but flawed. A better vaccine could be administered in fewer doses, the expert panel said.

What To Do

To learn more about the anthrax vaccine, visit the Defense Department's Anthrax Vaccine Immunization Program. To see what the Food and Drug Administration has to say about the vaccine, click here.

For a critical view of the anthrax vaccine, try this page produced by the American Gulf War Veterans Association.

SOURCES: Maj. Andrew Wiesen, M.D., M.P.H., chief, epidemiology and disease control, Madigan Army Medical Center, Tacoma, Wash.; Philip Tierno, Ph.D., director of clinical microbiology, New York University School of Medicine and Mount Sinai School of Medicine, New York City; March 27, 2002, Journal of the American Medical Association
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