Pregnancy provides an opportunity for evaluation of a woman's immunization status. Pregnant women are a vulnerable population. They have an altered immune response and, for some infections, are at increased risk of infection and at increased risk of severe outcomes once infected. The fetus, neonate and young infant can also be impacted by infections that can results in congenital abnormalities or severe illness.
One of the challenges of developing recommendations for pregnant and breastfeeding women is the lack of studies that would allow making evidence-based decisions. Only a few methodologically robust studies of vaccine administration in pregnant and breastfeeding women exist; most safety data available are derived from registries where outcomes are passively reported.
When considering vaccination for pregnant or breastfeeding women, it is important to distinguish between live and inactivated vaccines. There is no theoretical reason to suspect that inactivated vaccines would be associated with an increased risk of adverse events when administered during pregnancy or in breastfeeding women. Live vaccines, however, such as measles, mumps, rubella, varicella, and yellow fever, should generally not be given during pregnancy because of the theoretical risk of harm to the foetus if transmission of the vaccine virus to the fetus occurs.
Ideally, the immunization status of women intending to become pregnant should be reviewed and vaccines updated as necessary prior to conception. Live vaccines, for example, can be given to non-pregnant women with the advice to avoid pregnancy for at least 28 days following immunization. Some pregnancies are unplanned, however, and immunization status will need to be assessed during the pregnancy.
Maternal Benefits
The objective of vaccination during pregnancy is to protect the mother and, potentially, the fetus and newborn. Pregnant women respond adequately to vaccines even though pregnancy is an immunologically altered state. Clinical trials of tetanus toxoid and inactivated polio vaccine administered during pregnancy have demonstrated normal adult immunologic responses. Vaccines recommended for the protection of a pregnant woman's health include:
inactivated influenza vaccine
hepatitis B vaccine for a woman with ongoing exposure risks
hepatitis A vaccine for a woman who is a close contact of a person with hepatitis A or who is travelling to an endemic area
tetanus toxoid and reduced diphtheria toxoid-containing vaccine if indicated
meningococcal vaccine in an outbreak setting or post-exposure
pneumococcal polysaccharide or conjugate vaccine for women in a high risk group due to underlying illnesses
acellular pertussis-containing vaccine (Tdap) for all pregnant women who are 26 weeks of pregnancy or greater who have not previously received Tdap vaccine in adulthood ; imunization should not be delayed until close to delivery since this may provide insufficient time for optimal transfer of antibodies and direct protection of the infant against pertussis
Maternal Safety
Inactivated vaccines are generally safe in pregnancy. Reactions following vaccination with inactivated vaccines are usually limited to the injection site. No increase in anaphylactic reactions or events that might induce preterm labour has been observed. Vaccines that contain thimerosal are considered safe in pregnancy and the National Advisory Committee on Immunization (NACI) has concluded that there is no safety reason to avoid the use of thimerosal-containing vaccines for pregnant women.
Benefits of Immunization in Pregnancy for the Fetus and Infant
The beneficial effects of maternal vaccination for the newborn have been well documented. Maternal vaccination protects the mother from vaccine-preventable diseases that she otherwise may transmit to her fetus or infant. In addition, protective concentrations of maternal antibodies may be transferred to the fetus transplacentally, with the majority of transfer occurring during the third trimester. Maternal antibodies typically have a half-life of 3 to 4 weeks in the newborn, and progressively decrease during the first 6 to 12 months of life. Recommended infant immunization schedules take into consideration the potential effect that maternally transferred antibodies may have on infant vaccinations.
Safety of Immunization in Pregnancy for the Fetus/Infant
There is no theoretical reason to suspect that adverse events will occur in the fetus or infant following maternal vaccination with inactivated vaccines during pregnancy. There are no published data indicating that currently authorized inactivated vaccines are teratogenic or embryotoxic, or have resulted in specific adverse pregnancy outcomes.
In general, live attenuated viral or bacterial vaccines are contraindicated in pregnancy, as there is a theoretical risk to the fetus; however, when benefits outweigh risks, vaccination with a live attenuated vaccine may be considered (e.g., yellow fever vaccine in a pregnant woman travelling to an endemic area).
Imunization During Pregnancy (refer to Table 1)
Recommended vaccines
Inactivated influenza vaccine
All pregnant women, at any stage of pregnancy, should be considered high priority for receiving inactivated influenza vaccine, because of their increased risk of influenza-associated morbidity, evidence of adverse neonatal outcomes associated with maternal influenza, evidence that vaccination of pregnant women protects their newborns from influenza and influenza-related hospitalization, and evidence that infants born during the influenza season to vaccinated women are less likely to be premature, small for gestational age, and low birth weight. Live attenuated influenza vaccine should not be given to pregnant women, as discussed in the previous section.
There is good evidence demonstrating the safety of inactivated influenza vaccine during pregnancy. Active surveillance following influenza vaccination during pregnancy has not shown evidence of harm to the mother or fetus associated with influenza immunization. Although the cumulative sample size of these studies is relatively small, particularly for immunisation in the first trimester, passive surveillance has not raised any safety concerns, despite widespread use of influenza vaccine in pregnancy over several decades. Surveillance following the use of both adjuvanted and unadjuvanted pH1N1 vaccine in more than 100,000 pregnant women in Canada and almost 500,000 pregnant women in Europe did not reveal any safety concerns.
Women who did not receive influenza vaccination during pregnancy should receive influenza vaccine post-partum before discharge from hospital if it is influenza season.
Refer to Influenza Vaccine in Part 4 for additional information.
Hepatitis B vaccine
All pregnant women should be routinely tested for hepatitis B surface antigen (HBsAg). A pregnant woman who has no markers of hepatitis B (HB) infection but who is at high risk of HB should be offered a complete HB vaccine series at the first opportunity during the pregnancy and should be tested for antibody response. HB vaccine can be used safely in pregnancy and should be administered when indicated, because acute HB in a pregnant woman may result in severe disease for the mother and chronic infection in the infant. The safety of combined hepatitis A-hepatitis B vaccine given during pregnancy has not been studied in clinical trials; however, there is no theoretical reason to suspect an increased risk of adverse events to mother or infant. Refer to Hepatitis B Vaccine in Part 4 for additional information.
Vaccines that may be indicated
Hepatitis A vaccine
The efficacy and safety of hepatitis A vaccines given during pregnancy has not been studied in clinical trials, but there is no theoretical reason to suspect an increased risk of adverse events to the mother or the infant. Hepatitis A can cause severe disease in pregnancy, and the vaccine should be considered for pregnant women when potential benefits outweigh risks, such as for post-exposure prophylaxis or for travel to high risk endemic areas. Refer to Hepatitis A Vaccine in Part 4 for additional information.
Tetanus toxoid, diphtheria toxoid, acellular pertussis vaccines
Susceptible pregnant women may receive tetanus toxoid-reduced diphtheria toxoid-containing vaccine (Td) if indicated. Follow-up data on pregnant women who have received tetanus toxoid-containing vaccine (often in the first trimester) have not revealed an increased risk of adverse events. There is no theoretical reason to suspect an increased risk of adverse events to mother or infant following the administration of Td vaccine.
Immunization with Tdap to date has been shown to be safe in pregnant women and allows high levels of antibody to be transferred to newborns during the first two months of life when the morbidity and mortality from pertussis infection is the highest. All pregnant women at 26 weeks of pregnancy or later, who have not received a dose of pertussis-containing vaccine in adulthood, should be encouraged to receive Tdap vaccination. Immunization should not be delayed until close to delivery since this may provide insufficient time for optimal transfer of antibodies and direct protection of the infant against pertussis. In special circumstances, such as a pertussis outbreak, all pregnant women who are 26 weeks gestation or greater may be offered Tdap vaccination, irrespective of their immunization history based on the advice of local public health officials. Refer to Tetanus Toxoid, Diphtheria Toxoid and Pertussis Vaccine in Part 4 for additional information.
Top of PagePoliomyelitis vaccine
Inactivated poliomyelitis vaccine (IPV) may be considered for pregnant women who require immediate protection and are at increased risk of exposure to wild poliovirus. Limited data have not revealed an increased risk of adverse events associated with IPV vaccine administered to pregnant women. There is no theoretical reason to suspect an increased risk of adverse events to mother or infant following IPV administration. Refer to Poliomyelitis Vaccine in Part 4 for additional information.
Pneumococcal vaccine
Recommendations for pneumococcal vaccines in pregnancy and for breastfeeding women are the same as for non-pregnant and non-breastfeeding adults. Pneu-P-23 is recommended for adults at high risk for invasive pneumococcal disease; additionally, Pneu-C-13 is recommended for adults who are immunocompromised. There is no evidence to suggest a risk to the fetus or to the pregnancy from maternal immunization with inactivated vaccines, therefore, women who are breastfeeding can be vaccinated with Pneu-P-23 or Pneu-C-13 vaccine, if indicated. Refer to Pneumococcal Vaccine in Part 4 and Immunization of Immunocompromised Persons and Immunization of Persons with Chronic Diseases in Part 3 for additional information.
Meningococcal vaccine
Conjugate meningococcal vaccines have not been studied in pregnancy; however, there is no theoretical reason to suspect adverse events to mother or infant will occur and may be given in circumstances when the benefits outweigh the risks. Conjugate meningococcal vaccine should be considered for pregnant women in circumstances such as travel to a high risk area; post-exposure prophylaxis against a vaccine preventable strain if indicated; or during an outbreak if indicated. Refer to Meningococcal Vaccine in Part 4 for additional information.
Rabies vaccine
If a pregnant woman has had a potential exposure to rabies, post-exposure prophylaxis should be given. If pre-exposure prophylaxis is indicated for work or travel purposes, in general, avoidance of risk should be considered and pre-exposure immunization delayed unless substantial risk of exposure remains. Refer to Rabies Vaccine in Part 4 for additional information.
Other inactivated vaccines
Cholera and travellers' diarrhea vaccine, and Japanese encephalitis vaccine have not been studied in pregnant women. Administration of either vaccine to pregnant women may be considered only in high risk situations after evaluation of the benefits and risks. Inactivated parenteral typhoid vaccine should be used in high risk situations if protection against typhoid is required. Refer to vaccine specific chapters in Part 4 for additional information.
Vaccines not recommended
Human papillomavirus vaccine (HPV)
HPV vaccine is not recommended for use in pregnancy because data on efficacy and safety of HPV vaccination in pregnancy are limited. No adverse outcomes of pregnancy or adverse events to the developing fetus have been reported. Initiation of the HPV vaccine series should be delayed until after completion of pregnancy. If a woman is found to be pregnant after initiating the vaccination series, completion of the series should be delayed until after pregnancy. If a vaccine dose has been administered during pregnancy. No intervention is required if vaccine has been administered during pregnancy. Refer to Human Papillomavirus Vaccine in Part 4 for additional information.
Generally contraindicated vaccines
Measles-mumps-rubella vaccine
Measles-mumps-rubella vaccine (MMR live attenuated vaccine) is generally contraindicated in pregnancy because there is a theoretical risk to the fetus. However, in some situations, potential benefits may outweigh risks, such as during measles or rubella outbreaks, in which case vaccination may be considered. There is no evidence to date demonstrating a teratogenic or other risk from MMR vaccine. Inadvertent immunization with MMR vaccine is not a reason for pregnancy termination.
Pregnant women without documented evidence of prior immunization with a rubella-containing vaccine should be serologically screened for rubella antibodies. Those found not to be immune on serological testing should be vaccinated with one dose of MMR vaccine in the immediate post-partum period, before discharge from hospital (unless they have received Rh immune globulin [RhIg] - refer to Rh immune globulin and MMR vaccine). Women who have been appropriately immunized post-partum do not need to be serologically screened for rubella antibodies, either post-immunization or in subsequent pregnancies. Women who have been found to be serologically positive in one pregnancy do not need to be screened again in subsequent pregnancies.
Refer to Measles Vaccine, Mumps Vaccine, and Rubella Vaccine in Part 4 for additional information.
Univalent varicella vaccine
Varicella vaccine (a live attenuated vaccine) is contraindicated in pregnancy because there is a theoretical risk to the fetus; however, there is a lack of evidence to demonstrate a teratogenic or other risk from varicella vaccine. Inadvertent immunization with varicella vaccine is not a reason for pregnancy termination.
Pregnant women without documented evidence of prior immunization with 2 doses of varicella vaccine or evidence of varicella disease should be serologically screened for varicella antibodies. Those found to be susceptible to varicella should receive 2 doses of a univalent varicella vaccine, 6 weeks apart; the first dose should be given in the immediate post-partum period, before discharge from hospital (unless they have received Rh immune globulin [RhIg] - refer to Rh immune globulin). Once appropriately immunized, there is no need for serological confirmation of immunity.
Refer to Varicella (Chickenpox) Vaccine in Part 4 for additional information, including post-exposure prophylaxis with varicella zoster immune globulin for pregnant women exposed to varicella.
Other live attenuated vaccines
The use of other live attenuated vaccines during pregnancy must be evaluated on the basis of the individual risk and benefit. Live attenuated oral typhoid vaccine is contraindicated in pregnancy because of the lack of data on safety or efficacy; inactivated typhoid vaccine should be used if indicated. Live attenuated intranasal influenza vaccine should not be given to pregnant women; inactivated influenza vaccine should be used if indicated. Live oral polio vaccine (OPV) should not be administered to pregnant women; inactivated polio vaccine should be used if indicated. In addition, OPV is not available in Canada. BCG vaccine has not been studied in pregnant or breastfeeding women. BCG vaccine should not be given during pregnancy although no harmful effects of BCG vaccination on the fetus have been observed.
If a pregnant woman must travel to an area at high risk of yellow fever transmission and a high level of mosquito protection is not feasible, yellow fever (YF) vaccine may be administered when the risk of exposure is high and the travel cannot be postponed. In one study of women given YF vaccine early in pregnancy, there was slight increased risk of minor malformations (mainly skin) in the babies; no increased risk of major malformations was found. Since seroconversion rates following YF vaccine are lower during pregnancy; post-immunization serology should be considered. Inadvertent immunization with YF vaccine is not a reason for pregnancy termination.
Smallpox vaccine may be considered for a pregnant woman in the highly unlikely event of a high risk exposure.
Refer to vaccine specific chapters in Part 4 for additional information.
Live attenuated vaccines and Rh immune globulin
A risk-benefit assessment is needed for post-partum women who have received RhIg and require MMR or varicella vaccine. Immune globulin administration may impair the efficacy of live attenuated vaccines, such as MMR and varicella, as measles, rubella, and varicella antibodies may be present in the RhIg preparation. The risk of lowered vaccine efficacy in the long term needs to be weighed against the need for protection in the short-term. To optimize response to vaccine, rubella-, measles- or varicella-susceptible women who receive RhIg in the peri-partum period should generally wait 3 months before being vaccinated with MMR or varicella vaccine.
However, if there is a risk of exposure to rubella, measles, or varicella, a risk of recurrent pregnancy in the 3-month post-partum period, or a risk that vaccines may not be given later, MMR, univalent varicella vaccines or both may be given prior to discharge with a second dose at the recommended interval if indicated. If only one dose is needed, serologic testing for rubella and varicella should be done 3 months later and women who have not mounted an antibody response should be revaccinated. In the event that a post-partum woman receives MMR or varicella vaccines prior to receiving RhIg and a second dose is not indicated, serologic testing for rubella, varicella or both should be done 3 months later and the woman revaccinated if she has not mounted an antibody response.
Biologic products during pregnancy
There is no known risk to the fetus or pregnant woman from administration of immune globulin for passive immunization. Immune globulin products should be administered to pregnant women as required.
In general, women should not receive immune modulators, such as infliximab or rituximab, during pregnancy. IgG immunoglobulins are known to pass the placental barrier and there is a risk that this treatment could deplete B-cells in both pregnant women and their fetus. It is particularly important not to administer live vaccines to pregnant women who receive monoclonal antibodies, such as TNF inhibitors. Refer to Immunization of breastfed infants for additional implications for the infant.
In general, women should not receive immune modulators, such as infliximab or rituximab, during pregnancy. IgG immunoglobulins are known to pass the placental barrier and there is a risk that this treatment could deplete B-cells in both pregnant women and their fetus. It is particularly important not to administer live vaccines to pregnant women who receive monoclonal antibodies, such as TFN inhibitors. Refer to Immunization of breastfed infants for additional implications for the infant.
Immunization of Household Contacts of Pregnant Women
A pregnant household member is not a contraindication for routine vaccination of her household contacts. On the contrary, pregnancy should be used as an opportunity to update immunization of susceptible household contacts. MMR and varicella-containing vaccines should be administered when indicated to children and other household contacts of pregnant women. Infants living in households with a pregnant woman can be vaccinated with rotavirus vaccine, as indicated. The risk of infection and disease from rotavirus vaccine virus is low because most women of childbearing age have pre-existing immunity to rotavirus through natural exposure and rotavirus infection during pregnancy is not known to pose a risk to the fetus.
In the unlikely event of vaccination against smallpox, extreme precautions should be taken for unvaccinated pregnant household and other close contacts of persons receiving smallpox vaccine to eliminate viral transfer to these contacts. Such precaution can include isolation of the vaccinee from his or her pregnant household contacts until the vaccine scab falls off.
Immunization during Breastfeeding (refer to Table 1)
Immunization of breastfeeding women
In general, routinely recommended vaccines may be safely administered to breastfeeding women. There are limited data available regarding the effects of maternal vaccination on breastfed infants; however, there have been no reported adverse events thought to be vaccine-related. There is no evidence that immunization during breastfeeding will adversely influence the maternal or infant immune response.
Annual influenza vaccination is recommended for breastfeeding women. Live attenuated influenza vaccine has a similar or lower immune response than inactivated influenza vaccine in adults; inactivated vaccine is preferred if the breastfeeding woman has a chronic health condition.
Women who are breastfeeding can be vaccinated with Td, Tdap, pneumococcal, meningococcal, hepatitis A, hepatitis B, IPV, rabies, typhoid, MMR, varicella and cholera vaccines, if they are indicated. HPV vaccine may be administered to breastfeeding women.
Japanese encephalitis (JE) vaccine has not been studied in breastfeeding women. Administration of JE vaccine to breastfeeding women who must travel to areas where the risk of JE infection is high should be immunized only if the risk of disease outweighs the unknown risk of vaccination to the woman and her breastfeeding infant.
There are a few instances when vaccination is not recommended during breastfeeding. Probable transmission of yellow fever vaccine strain virus from a mother to her infant through breastfeeding has been reported; therefore, breastfeeding mothers should not generally be vaccinated with yellow fever vaccine , unless potential benefits outweigh risks, such as travel to areas in which the risk of transmission is high and mosquito protection is not feasible. It is not known whether BCG vaccine is excreted in human milk. Because live vaccine may be excreted in human milk, caution should be exercised when considering BCG vaccine while breastfeeding. Smallpox vaccine is not recommended for breastfeeding women because of the theoretical risk for contact transmission from mother to infant. If smallpox vaccine is used for any reason in a breastfeeding woman, breastfeeding and other close contact with the baby should be avoided until the scab has separated from the vaccination site.
Refer to vaccine specific chapters in Part 4 for additional information.
Immunization of breastfed infants
In general, infants who are breastfed should receive all recommended vaccines according to the routine immunization schedule. In developed countries, there is no evidence that transfer of antibodies in human milk can affect the efficacy of live attenuated vaccines in breastfed infants.
The one exception to this recommendation is for breastfeeding women who are receiving immunosuppressive monoclonal antibodies (such as infliximab or rituximab), or who were on these drugs during pregnancy. Because monoclonal antibodies are excreted in human milk, women should be advised to discontinue nursing until circulating drug levels are no longer detectable. Infants who have been exposed to monoclonal antibodies, either during pregnancy or from breastfeeding, should not receive BCG vaccine at birth and should have B cell enumeration. B cell enumeration should be normal before vaccination with BCG or live vaccines. Consultation with an immunologist is advised.
Refer to Immunization of Immunocompromised Persons in Part 3 for additional information regarding monoclonal antibodies and immunization.
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