Smallpox vaccination is not recommended for pregnant women because it can be fatal to a developing fetus.
The United States initiated a campaign to vaccinate healthcare workers against smallpox in January so they could be prepared to treat victims in the event of a bioterrorist attack. The military began vaccinating many of its personnel in December.
As part of those programs and research studies of the vaccine, 103 women who were pregnant or became pregnant within four weeks of inoculation accidentally received the smallpox vaccine, researchers from the CDC and the Department of Defense reported in the May 2 issue of the CDC's journal Morbidity and Mortality Weekly Report.
Although vaccinia, the virus in the smallpox vaccine, is not smallpox and cannot cause the disease, it can be harmful to fetuses as well as to people with certain conditions such as eczema and immune disorders.
The researchers note that the main concern among the pregnant women is that the "smallpox vaccine can cause fetal vaccinia, a rare but serious complication of exposure to the vaccine during pregnancy that often results in fetal or neonatal death and premature birth."
Of the 103 women who received the smallpox vaccine, 85 were in the military, 6 were civilian healthcare workers and 12 were participating in research studies of the vaccine.
The CDC is uncertain if any of the fetuses has been affected by fetal vaccinia, Dr. Jane Seward, chief of the agency's viral vaccine preventable diseases branch, told United Press International.
"It's very unlikely given how low the risk is that we will see a case," Seward said.
Fetal vaccinia is so rare that only 50 cases have ever been reported, including three that occurred in the United States before naturally occurring smallpox was globally eradicated and the vaccine was still routinely given to people, including pregnant women. Two of the U.S. infants died, and one survived and developed normally.
To prevent fetal vaccinia from occurring, the CDC and state health departments as part of the vaccination program caution vaccinees who are pregnant or considering becoming pregnant not to be vaccinated. Health officials warn about the risks posed to the fetus and also ask women about the date of their last menstrual period, recommend contraception and offer or advise pregnancy tests before they receive the vaccine.
President Bush's original vaccination plan called for inoculating up to 10 million healthcare workers and first responders, such as emergency medical personnel, firemen and police.
So far only about 500,000 military personnel and civilians have received the vaccine. If the CDC moves forward and begins to vaccinate more people, some vaccine experts expect to see more cases of pregnant women inadvertently getting inoculated.
"This is an unwanted consequence of vaccination and part of what many of us in public health have been concerned about," Dr. William Schaffner, who is chairman of Vanderbilt University's Department of Preventive Medicine at Vanderbilt University Medical Center in Nashville, told UPI.
"I'm absolutely convinced that if we move into phase 2 (of the vaccination program) there will be many more of these," said Schaffner, who serves on the CDC's Advisory Committee on Immunization Practices.
"Even among healthcare workers you can see there were inadvertent vaccinations of pregnant women and we can anticipate, if the vaccination program is opened up roughly speaking to 10 million people ... we will get a disproportionately large number of people vaccinated who might be pregnant," Schaffner said.
One reason for this is "the education and screening activities are not likely to be as rigorous as phase 1," he said. Another factor is that police and firemen may be less likely than healthcare workers and military personnel to properly wear protective bandages over the vaccination site to prevent shedding of the virus, he said.
And a third problem is just the sheer volume of people being vaccinated. "Many of us (in public health) anticipate there will be more instances of secondary transmission (of the vaccine virus) when you vaccinate a larger number of people," Schaffner said.
Seward said the CDC is "concerned seeing any (cases of pregnant women being vaccinated), which is why we're looking at this to see if there's anything we can do to reduce this even further."
But she noted that pregnancy screening and the educational efforts about the risks posed to fetuses "has effectively reduced the cases a lot from what we might expect without such procedures in place."
"It might be there's no way to reduce them lower," she said.
The CDC said the military has revised its educational materials for those getting vaccinated and expanded the questions concerning pregnancy on screening forms. The CDC said women being vaccinated should take a pregnancy test the day of the inoculation, but the agency noted that these tests might miss very early pregnancies.
Of the six civilian women who were vaccinated, two became pregnant approximately one week before receiving the vaccine and the remaining four became pregnant within a month afterwards. Two had miscarriages but the smallpox vaccine is not thought to cause this or any serious birth defects besides fetal vaccinia.
The CDC will continue to follow the other four civilian women for "outcomes during pregnancy and right up to term (and) all babies born will be tested for vaccinia at delivery," Seward said.
The Defense Department will monitor the status of the 85 women who inadvertently received the vaccine in its program, which between December 2002, and April 22, 2003, had vaccinated 52,185 women of childbearing age. The department did not respond to inquiries from UPI by press time.
Of the 85 pregnant women who received the vaccine, 62 conceived before vaccination and 23 conceived within 4 weeks following inoculation, the CDC said.
An additional 12 women received the vaccine during their pregnancy while enrolled in clinical studies from November 2001 through April 24, 2003. All of these women had a negative pregnancy test on the day of vaccination, the CDC said.
Officials are also concerned about another two pregnant civilian women who had close contact with people who had recently been vaccinated. The CDC recommends pregnant women avoid close contact -- such as sharing the same bed -- with recently vaccinated individuals for 28 days due to the risk of these people shedding the vaccine virus and infecting the women.
Neither of the two women has displayed any symptoms of vaccinia exposure, however.
(Reported by Steve Mitchell, UPI Medical Correspondent, in Washington)