A number of vaccines, especially live-virus vaccines, should not be given to pregnant women because they may be harmful to the baby. A live-virus vaccine, as the name implies, is made using the live strains of a virus. Some vaccines can be given to the mother in the second or third trimester of pregnancy, while others should only be administered either at least three months before the baby is born or immediately after birth.
The Whole Patient interviewed Kenneth E. Johnson, DO, to get his input on vaccines and pregnancy. Dr. Johnson is vice chair of the Department of Obstetrics and Gynecology; associate professor of obstetrics and gynecology and public health; and director of the Women's Health Center at Nova Southeastern University College of Osteopathic Medicine in Fort Lauderdale, Fla. In addition, Dr. Johnson is a fellow of the American College of Osteopathic Obstetricians and Gynecologists.
Is it safe to get vaccines during pregnancy?
Dr. Johnson: The simple answer is “yes” but the important concept here is that the list of vaccines recommended during pregnancy is relatively small.
For the most part, the only vaccines recommended during pregnancy are primary or booster doses of adult-type tetanus and diphtheria toxoids, and both the inactivated seasonal and H1N1 influenza vaccines. Because of the increased number of deaths in pregnancy from the H1N1 flu, a very strong recommendation has been made for vaccination during pregnancy with the H1N1 vaccine.
Which vaccines are the most important to get before getting pregnant?
Dr. Johnson: This is a very important question because it reminds us all of the importance of the preconceptual visit. Getting important vaccines for the health of the mother and baby before pregnancy helps avoid the concerns about teratogenicity and pregnancy complications that may be caused by vaccines given after a woman discovers she is pregnant. Furthermore, maternal immunity established in the mother may have more time to be passed on to the baby.
The Infectious Diseases Society of America has published general guidelines for immunization of pregnant women, and the immunizations that are very important for women who may become pregnant—measles, mumps and rubella. Once vaccinated with these important vaccines prior to pregnancy, a woman should avoid getting pregnant for at least 28 days after she first receives these vaccines.
What vaccines do you suggest avoiding during pregnancy?
Dr. Johnson: Here the principal of “do no harm” applies. In general, live vaccines have some potential for infecting the baby if given during pregnancy. Although serious harmful effects have not been well documented in babies of mothers who have received live vaccines during pregnancy, subclinical infections have been documented and for this reason live vaccines should be avoided. Furthermore, even though the quadrivalent HPV vaccine does not contain live virus, its use in pregnancy is not recommended. The measles, mumps and rubella vaccines are contraindicated during pregnancy as mentioned above. Finally, the varicella vaccine is also a live virus vaccine and should not be given to women who are currently pregnant. (From ACIP guidelines).
What if a patient got a vaccine and didn't know that she was pregnant?
Dr. Johnson: Fortunately, here the news is mostly good news. This event of course happens all the time and in general the risk of the vaccine causing a birth defect or miscarriage is very low but not zero. In our practice, we inform the patient of the same and in general termination is not recommended. In the case of the human papillomavirus (HPV) vaccine, a birth defects registry has been established and thus far there has not been an increased incidence of birth defects in women who have been inadvertently vaccinated while already pregnant.
If a woman is found to be pregnant and has received the vaccine, she should not receive any further vaccine doses during the pregnancy and the final doses should be given after the completion of the delivery of the baby.
How do you deal with the concern over mercury and thimerosal in vaccines?
Dr. Johnson: This is a very emotional issue for everyone, but in general the news is very good. Despite many parents' understandable concerns, to date there is no evidence to suggest a scientific link between the thimerosal and mercury in vaccines and autism and other chronic diseases.
Many excellent studies on the safety of vaccines containing thimerosal have shown the pre-vaccination blood mercury levels in 6-month-olds were not higher than those in 2-month-olds, suggesting that exposure to thimerosal-containing vaccines does not result in an accumulation of mercury in the blood of vaccinated children. In these studies, the concentration of mercury in the blood was less than the concentration that is thought to be safe in cord blood. Furthermore, it is very important to note that the ethylmercury in thimerosal-containing vaccines is rapidly eliminated from the blood of infants who receive these vaccines.
If you vaccinate a woman while she is pregnant, does the fetus develop immunity as well?
Dr. Johnson: In general, the answer is “yes.” When a mother develops antibodies from a previous infection, like herpes for example, the mother then does, in fact, pass on beneficial antibodies to the baby during pregnancy. Likewise, certain antibodies that increase after maternal immunization do cross the placenta and protect the baby.
What are some of the questions your pregnant patients have about vaccines and how do you address them?
Dr. Johnson: Many pregnant women are worried that the vaccines like H1N1 and the seasonal influenza vaccine may cause harm to their babies. We tell them that there is essentially no evidence that these lifesaving vaccines given during pregnancy cause any problems in the baby.
Several national registries have maintained this data and it is very reassuring. More importantly, we stress that in the case of an H1N1 infection during pregnancy, many women have in fact died so the benefit of the vaccine during pregnancy far outweighs any risk. We stress that if the mom dies, the baby dies, so we must keep mom healthy even if there is some small risk to baby.
Are there conditions pregnant women might have that would stop you from giving a vaccine?
Dr. Johnson: Certainly in conditions where a mother was ill and the diagnosis was pending, I would delay certain vaccinations. An important exception to this approach would be in the event of a potential rabies exposure during pregnancy. Pregnancy is not a contraindication to the administration of the rabies vaccine because the vaccine is made from inactivated virus, and failure to administer could be life threatening.
Kenneth E. Johnson, DO, serves as an associate professor in the department of obstetrics and gynecology and the department of public health at the Nova Southeastern University College of Osteopathic Medicine (NSU-COM) in Fort Lauderdale, Fla. Dr. Johnson, who is board certified by the American Osteopathic Board of Obstetrics and Gynecology, is also the director of NSU's Women's Health Center. He can be reached at: kjohnson@nova.edu.