Immunizations

We are commonly asked questions regarding immunizations, their effect on pregnancy and their impact on infertility therapy. We have prepared this document to hopefully answer some of your basic questions. If you have questions regarding your immunity to a specific pathogen, please contact your primary care provider so that your immunization records may be reviewed and any testing that needs to be done may be initiated.

Immunization is the process by which your immune system is sensitized to a particular disease, so that if you are exposed to the disease, your immune system will recognize the foreign invader and eliminate the infection. There are primarily two types of pathogens that we concern ourselves with: viruses and bacteria. Viruses must live within a host's cell to be "active" and reproduce. Bacteria, on the other hand, are single celled organisms that are able to live and reproduce independently. Bacteria can be treated by antibiotics, while viruses cannot. Our ability to treat viruses is improving with the development antiviral medicines, but there remain significant limitations to anti-viral therapy. Vaccines are the process by which we can immunize individuals. Immunization can also occur by actually having the disease.

The basic principle of vaccines is that a substance is injected into the body to either stimulate or supplement the immune system. There are 4 types of vaccine preparations used in the United States for immunization. First, there are "toxoid" preparations. These are toxins from the bacteria that have been chemically altered to not cause illness but still can stimulate an immune response. Second are "inactivated vaccines". These contain the actual microorganism (virus or bacteria), but it has been killed chemically or by heat. They cannot cause infection, but still can stimulate the immune system. The third types of vaccines are "live" vaccines. These preparations contain an actual live virus or bacteria that have been specially grown so it cannot cause disease, but can still cause your immune system to respond to an infection by its virulent counterpart. Finally, there are "immune globulin" preparations, which contain actual antibodies against a particular disease. Toxoids, inactivated and live vaccines are considered "active immunization" because they activate your immune system. They are generally long lasting (years to life-time). The immune globulins are considered "passive immunization" because the end product of the immune activation is supplied (the antibodies) and immune system is not activated (for example, chicken pox vaccination). Passive immunization lasts only about 30 days. However, passive immunization may be necessary when a woman is exposed to an infectious agent or toxin and her own immune system will not have time to develop their own antibodies.

In general, most physicians try to avoid vaccination during pregnancy with any live bacterial or viral product. However, it is important to note that the risks of vaccination are largely theoretical, so that when the potential risks of vaccination in women with clear indications are outweighed by the risks of the disease, vaccination during pregnancy is often appropriate. None of the vaccines listed on the next page have any confirmed risk to a fetus. There is no evidence that vaccines impair fertility in any way.

Ideally, all women of childbearing age should be immune to measles, mumps, rubella, tetanus, diphtheria and polio. This can occur through vaccination or through natural infection. A documented history of vaccination or serologic evidence of any detectable antibody is adequate. Clinical diagnosis is generally not considered accurate because other diseases may mimic the signs and symptoms of some of these illnesses.

Disease
Pathogen
  Risk to Mother Risk to Fetus Type of Immunizing Agent (vaccine) Pregnancy Delay After Vaccine Comments
Rubella Virus Low High risk of miscarriage and congenital defects Live attenuated virus 1 month Single dose vaccine combined with mumps and measles. Recommended wait after vaccine recently changed by CDC from 3 to one month
Measles Virus Significant High risk of miscarriage; congenital defects can occur Live attenuated virus 1 month  
Mumps Virus Low ? Increase miscarriage rate Live attenuated 1 month  
Influenza Virus Can be significant ? Increase miscarriage rate. No anomalies yet noted Inactivated virus none CDC recommends vaccination for any woman who will be pregnant and in the third trimester during flu season
Hepatitis Virus Can be significant particularly in third trimester Can be transmitted to neonate as either full blown infection or carrier state Inactivated virus none Used with hepatitis B immune globulin in cases of exposures
Tetanus diphtheria Bacteria Severe: tetanus mortality 30%, diphtheria mortality 10% Neonatal tetanus mortality 60% -Toxoids
-Immune globulin
none Vaccine clearly prevents neonatal tetanus. Booster needed every 10 yrs
Varcella (chicken pox) Virus Low indicated for prevention of congenital varicella attenuated virus
-Immune globulin
  doses 4-8 wks apart
Polio Virus Significant Very significant Live attenuated virus 1 month Most adults have been immunized.

If you have questions regarding your immunization status, please contact your primary care provider so that your immunization records can be reviewed or appropriate testing to see if you are immune can be initiated.


References

ACOG, Immunization During Pregnancy. Technical Bulletin #160, October 1991. In: The 2001 Compendium of Selected Publications, 546-555, 2001.

Amstey, MS. Immunization in Pregnancy. In: Meade PB, Hager DW, Faro S, eds; Protocols for Infectious Diseases in Obstetrics and Gynecology. Second Edition. Blackwell Science, Malden MA; 128-134, 2000.

ACOG/AAP. Guidelines for Perinatal Care. Fourth Edition. 1997.

Center For Disease Control, National Immunization Program, Vaccine Information Statements:

MMR: (12/16/98), Influenza (4/24/01),Hepatitis B, (7/11/01)Tetanus-diptheria (6/10/94), Varicella (12/16/98),

To contact the CDC National Immunization Program:

Phone: 1(800) 232-2522
Website: http://www.cdc.gov/vaccines/

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