It has been five years since the CDC's Advisory Committee on Immunization Practices, or ACIP, recommended that all women who are pregnant -- and those who may become pregnant -- during influenza season should be vaccinated. Yet immunization rates for this high-risk group remain alarmingly low.
According to the CDC(www.cdc.gov), only 13 percent of pregnant women who did not have another condition that put them at risk for complications from flu -- such as diabetes or heart disease -- were vaccinated against seasonal influenza during the 2006-07 season.
Confusion among patients and physicians, as well as concerns about vaccine safety, have contributed to low vaccination rates among these women, said the CDC and other sources. However, a study from the Rhode Island Department of Health found that physicians can have a big influence on uptake.
The Rhode Island study, which spanned the 2005-06 and 2006-07 flu seasons, reported that 62.9 percent of pregnant women who were offered the flu shot or whose physicians recommended they get the shot did so. Conversely, only 4.1 percent of pregnant women who were not offered vaccination or whose physicians did not recommend the vaccine were immunized during the same period.
The study found that less half of pregnant women -- 46.6 percent -- were offered the vaccination or were recommended for vaccination by their doctors.
Tony Fiore, M.D., M.P.H., medical officer in the CDC's Influenza Division, said confusion may stem from the fact that most other vaccines aren't routinely recommended for pregnant women. In fact, varicella; zoster; and measles, mumps and rubella vaccines are contraindicated during pregnancy, while pneumococcal, hepatitis A, hepatitis B and meningococcal vaccines are recommended during pregnancy only when other risk factors are present.
Doug Campos-Outcalt, M.D., M.P.A., the AAFP's liaison to the ACIP, said the 2003 introduction of live attenuated influenza vaccine, which is delivered in a nasal spray, added to the confusion about flu vaccination during pregnancy.
"We have two types of flu vaccine now, one of which is licensed for use in pregnancy and one which isn't," he said. "The live attenuated influenza vaccine is not, whereas the trivalent influenza vaccine -- which is the injection -- is. And it's perfectly safe to give in pregnancy."
Fiore said prescribing information that manufacturers include with flu vaccine also is a barrier for some physicians. These documents include disclaimers about the lack of animal reproductive studies that have been conducted on these products and uncertainties about fetal harm.
"The prescribing information that comes with the vaccine is not labeled in such a way to make providers very comfortable with it," Fiore said. "The problem is that there probably have not been enough studies about safety during pregnancy that have been published.
"What we do have is a very long track record of having safety, retrospectively, during pregnancy. Looking back at safety during pregnancy, we don't see issues with fetal toxicity during pregnancy for women who get vaccinated," said Fiore.
Overall, he added, the benefits of the vaccine outweigh its potential risks.
"There's a lack of appreciation for how severe influenza can be for pregnant women, and also pregnant women become contacts of a very high-risk person as soon as they give birth, because newborns are at very high risk for influenza complications," said Fiore. "Vaccinating late in pregnancy provides protection not only for the woman, but also for the newborn."
Campos-Outcalt, who is associate head of the department of family and community medicine and assistant dean for outreach and multicultural affairs at the University of Arizona College of Medicine, Phoenix, said recommendations for influenza vaccination will become less complicated.
"This will go away in the near future -- this whole confusion -- because we're moving down a path of universal recommendations for flu vaccine -- for virtually everybody unless contraindicated -- annually in the United States," he said. "That's two or three years away, probably."
At that point, according to Campos-Outcalt, the issue of identifying special populations of adults to vaccinate, or not, will largely go away. "Then we'll just have to work with some lingering misconceptions about safety of the vaccine during pregnancy," he said.