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Pregnancy provides a situation in which engagement in medical care may be greater than at any time in an otherwise healthy adult woman's life. It allows for evaluation of the woman's vaccine status as well as consideration of vaccines that may be beneficial to the neonate, if given to the woman, in order to decrease the risk of neonatal vaccine-preventable illness.
This chapter will review general issues regarding immunization in pregnancy, but particular issues will be addressed in vaccine-specific chapters. It is important that the obstetric care provider be familiar with both the potential risks of vaccination in pregnancy and the potential benefits in preventing disease at that time and providing neonatal protection. Ideally, this planning should occur before conception. If a woman of reproductive age presents with the intent to become pregnant, the adult immunization schedule should be reviewed and vaccines updated as indicated. For more information, please refer to the Recommended Immunization Schedules chapter.
Although pregnancy is an immunologically altered state, there are no data to support an inadequate response to vaccines. This is supported by data from trials of tetanus toxoid and polio vaccine in which normal adult immunologic responses were observed in pregnant women. There are a number of indications for immunization of pregnant women for the benefit of their own health. Recommendations include hepatitis B vaccine in a person with ongoing exposure risks, hepatitis A vaccine in a traveler or close contact of a person with hepatitis A, tetanus toxoid, meningococcal vaccine in an outbreak setting, and pneumococcal and influenza vaccines for all adult indications.
There does not appear to be any evidence of increased risk of adverse reactions to vaccines administered in pregnancy. Reactions to vaccines in pregnancy are usually limited to local reactions, and no increase in anaphylactic reactions or events that might induce pre-term labour has been observed.
A major issue to consider regarding immunization in pregnancy is the risk or benefit of the vaccine for the fetus or neonate. There are no published data showing that any of the currently approved vaccines are teratogenic or embryotoxic, or have resulted in specific adverse pregnancy outcomes.
In contrast, there are a good deal of data supporting the beneficial effects of antenatal vaccines on the prevention of disease in the neonate. In order for a vaccine to be beneficial to a neonate, a protective concentration of maternal antibody needs to be transferred to the infant transplacentally. It is known that all subclasses of IgG are transported from mother to infant across the placenta, but the majority of transfer occurs during the third trimester. Active placental transfer of IgG is specific and has variable efficacy. The mechanism is not well understood but can result in a range of cord blood levels that can be 20% to 200% of maternal levels. Maternal IgG typically has a half-life of 3-4 weeks in the newborn, waning during the first 6-12 months of life. Current pediatric vaccine schedules take into consideration the potential effect that maternally transferred antibodies may have on infant vaccinations and incorporate this into the vaccine schedules and dosing.
Risks associated with vaccines in pregnancy are primarily theoretical risks associated with the administration of live virus vaccines. There are circumstances in which vaccination with a live-attenuated product may be considered (e.g., yellow fever vaccine). If live vaccine is inadvertently given to a pregnant woman, termination of the pregnancy is not recommended (see specific chapters for details).
1. Live-attenuated vaccines
In general, live-attenuated virus vaccines (such as measles, mumps and rubella (MMR) or varicella) are contraindicated in pregnancy as there is a theoretical risk to the fetus. However, it is important to mention that to date, there is no evidence to demonstrate a teratogenic risk from such vaccines.
2. Inactivated viral and bacterial vaccines, toxoidsThere is no evidence to suggest a risk to the fetus or to the pregnancy from maternal immunization with these vaccines.
Breast-feeding is considered safe following immunization of the mother and has not been shown to adversely influence the maternal immune response. Therefore, breast-feeding does not represent a contraindication to any maternal immunization, and breast-feeding women who have not received all recommended adult immunizations may be safely immunized. Infants who are breast-fed should receive all recommended vaccines at the usual times.
There is no known risk to the fetus and/or mother from administration of immune globulin for passive immunization during pregnancy. Therefore, these products should be administered as required.
Table 7. Indication for Use in Pregnancy
Vaccine | Indication for use in pregnancy | Comment |
---|---|---|
Measles,mumps,and rubella (MMR) | Contraindicated Immunize susceptible women post-partum. |
No known fetal effects but live vaccine - theoretical risk. Not reason for termination of pregnancy. |
Varicella | Contraindicated Immunize susceptible women post-partum. |
No known fetal effects but live vaccine - theoretical risk. Not reason for termination of pregnancy. |
Poliomyelitis Salk (IPV) | Not contraindicated | To be considered if pregnant woman needs immediate protection (high- risk situation/travel). No known fetal effects. |
Yellow fever | Generally contraindicated unless travel to high-risk endemic area is unavoidable. | No data on fetal safety although fetuses exposed have not demonstrated complications. Not a reason for pregnancy termination. |
Influenza | Safe | No adverse effects. |
Rabies | Not contraindicated for post- exposure prophylaxis. | Prudent to delay pre-exposure immunization unless substantial risk of exposure. |
Hepatitis A | No apparent risk | To be considered in high-risk situations in which benefits outweigh risks. |
Hepatitis B | No apparent risk | Vaccine recommended for pregnant women at risk. |
Pneumococcal polysaccharide | No apparent risk | Vaccine recommended for pregnant women in high-risk categories. |
Meningococcal | Polysaccharide vaccine safe and effective in pregnancy. Conjugate vaccine: no data available. | Polysaccharide vaccine to be administered as per general guidelines for non-pregnant women. Conjugate - considered in situations in which benefit outweighs risk. |
Cholera | No data on safety. | To be used in high-risk situation only (e.g., outbreak). |
Typhoid | No data on safety. Some preparations are live. | To be considered only in high-risk cases (e.g., travel to endemic areas). |
Diphtheria/tetanus | No evidence of teratogenicity. | Susceptible women to be vaccinated as per general guidelines for non-pregnant women. |
Pertussis | Lack of data confirming the safety and immunogenicity of acellular pertussis vaccine in pregnant women | Warranted when the risk of disease outweighs the risk of vaccine both for the mother and the fetus |
Japanese encephalitis Live | No data on safety. | To be considered only in high-risk cases (e.g., travel to endemic areas if benefit outweighs risk). |
Vaccinia (smallpox) Live | Contraindicated | Has been reported to cause fetal infection. |
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