Immunization is an important part of general health and a consideration when a woman is trying to conceive or is already pregnant. Although it is important to stay up-to-date on all immunizations to protect one's self and others from disease, there are several immunizations that are particularly important to consider in relation to pregnancy and protection of the fetus and newborn. After a woman becomes pregnant (or sometimes during preconception counseling), a woman will be evaluated for immunity to several diseases that can affect a growing fetus. These include hepatitis B, rubella, varicella, and sometimes human papilloma virus (HPV).1,2 In addition, there are immunizations that are important to receive while pregnant, not only to protect the mother from disease but also to pass immunity through the placenta to the fetus, conferring protection after the child is born. These include the Tdap (tetanus toxoid, reduced diphtheria toxoid, acellular pertussis) vaccine and the inactivated influenza vaccine.1,3,4 This article addresses in detail both of these immunizations and other considerations about immunity during pregnancy.
Pregnancy increases a woman's susceptibility to a number of infectious conditions, highlighting the importance of remaining up-to-date on immunizations to protect both mother and fetus during pregnancy.3 There is also maternal transfer of immunity to the growing fetus, allowing protection of the newborn before he or she is able to receive his or her own vaccinations.3 The Advisory Committee on Immunization Practices (ACIP) recommends the delivery of two immunizations during pregnancy, the Tdap and the inactivated influenza vaccine.3 The Tdap vaccination should be given between 27 and 36 weeks gestation for maximal protection of both the mother and infant.3,4 The influenza vaccination should be given as early as possible when available for the season.3,4
Tetanus Toxoid, Reduced Diphtheria Toxoid, Acellular Pertussis (Tdap)
Pertussis (also known as whooping cough) is a respiratory infection that is caused by the bacteria Bordatella pertussis.5 It is highly contagious and can have a severe course, especially in the infant population.3 Pertussis has become more widespread in recent years, likely due to waning immunity from the vaccine over time in combination with refusal to vaccinate.5 In the United States, approximately 1,000 infants are hospitalized and between 5 and 15 infants die each year due to pertussis.6 Adults can also contract pertussis, but infants younger than age 3 months are at highest risk for having severe complications from it.3,6,7,8 More than 90% of deaths associated with pertussis occur in infants younger than age 6 months.9 As a result, there has been a push to provide better protection for those infants who have not yet had the opportunity to receive their vaccines, as infants do not receive their first DTaP (diphtheria toxoid, tetanus toxoid, acellular pertussis) until age 2 months.3
In 2006, a process called “cocooning” was recommended, in which all adolescent and adult caregivers and family members that will be near the infant receive the Tdap vaccine at least 2 weeks prior to interaction with the infant.3,7,8 This approach, however, proved to be difficult to enforce and did not improve transmission rates of pertussis to infants.6 It was difficult to ensure that everyone interacting with the infant was fully vaccinated. In one study, close adult contacts of the infant only had a vaccination rate of 32.1%, and when complete cocoons could be established, they only consisted of one or two people.7
In 2011, a new recommendation encouraged all women who had never received Tdap previously to get the vaccine during pregnancy.3,8 Then, in 2012, the recommendation was expanded to include that every woman should get the Tdap vaccine during every pregnancy, regardless of her previous vaccination history.2,3,5,6,8 Studies determined that the ideal timing of the immunization was between 27 and 36 weeks gestation to maximize both the maternal antibody response as well as the passive transfer of antibodies to the fetus.3,5,6,8,10 If a woman has never received the Tdap vaccine and did not get it during pregnancy, it is recommended that she get it immediately after pregnancy to contribute to the cocooning effect for the infant.1,2,3,8 It is important to note, however, that full immunity will not be in effect for 2 weeks after vaccination.6 If a woman gets the Tdap outside the optimal time frame during pregnancy, it does not need to be repeated. However, if it is given prior to pregnancy, the mother should receive another dose between 27 and 36 weeks.1,6,8
Ideally, a woman should receive the Tdap during pregnancy because this confers the best protection for the mother and the infant.6 Studies show that infants who are born to mothers who received the Tdap vaccine during pregnancy had significantly higher pertussis antibody concentrations that those who did not, both at birth and at age 2 months.6,9 In infants whose mothers had the vaccine prior to pregnancy, the antibodies in infants decline rapidly in the first 6 months and are generally undetectable by age 4 months.5 This suggests that by giving the Tdap to mothers during pregnancy, we can passively immunize infants until they receive their own immunizations at age 2 months. There are also data to suggest that even after the infant receives the DTaP vaccine at age 2, 4, and 6 months, there is still increased immunity in those whose mothers received the Tdap during pregnancy.5 This added protection may last for up to 1 year.5 A study done by Kaiser Permanente health system showed that maternal immunization with Tdap during pregnancy reduced the risk of pertussis by 91.4% in the first 2 months of life and 69% during the first year.5 Some studies have shown a slightly decreased concentration of diphtheria antibodies after the third dose of DTaP in infants whose mothers received Tdap during pregnancy, but this normalized after the fourth dose.9 Several studies have shown that there are no adverse events related to the Tdap vaccine being given during pregnancy.9
Influenza is a seasonal illness that circulates every year, and every pregnancy will overlap with the influenza season at some point. Because influenza is a widespread annual illness, exposure is common and affects up to 11% of pregnant women.3 Women who are pregnant and postpartum are at higher risk for complications and more severe illness if they contract influenza due to changes in the immune system and cardiopulmonary system during pregnancy.1,3,11 Influenza is also associated with fetal complications such as preterm delivery, fetal distress, growth restriction, and an increased risk of delivery via cesarean delivery.3 Passive transfer of antibodies to the fetus through maternal immunization is currently the only way to provide neonatal protection, as infants younger than age 6 months old cannot be vaccinated for influenza.3 Studies have shown reduced rates of influenza-related hospitalizations in infants younger than age 6 weeks whose mothers received the influenza vaccine.3 For this reason, it is recommended by the American College of Obstetrics and Gynecology as well as ACIP that women receive the inactivated influenza vaccine either prenatally or as soon as possible during influenza season.2,3,10 There have been no associated fetal or obstetric complications related to receiving the influenza vaccine.3
Historically, national rates of influenza immunization in pregnant women have been low (around 15%).3 This did improve during the H1N1 pandemic in 2009, with rates getting as high as 50% to 60%.3,11 There are several reasons for these low rates, including false beliefs about susceptibility to influenza, the potential severity of the disease, and also the effectiveness of the vaccine.3 In one group of women interviewed for a study in Georgia, 80% believed that the influenza vaccine could cause birth defects.3 Immunization with the influenza vaccine is also less likely in women in lower socioeconomic groups, with lower education levels, and in racial and ethnic minorities.3 The influenza vaccine has been shown to be safe for both mothers and fetuses when given during pregnancy.11 There is no association between the receipt of the vaccine and common obstetric complications such as gestational diabetes, gestational hypertension, preeclampsia, or chorioamnionitis.11
Other Immunization Considerations
Although there are certain medications and vaccines that are not recommended during pregnancy, there is no evidence of risk to the fetus or the pregnant mother when administering inactivated virus or bacterial vaccines or toxoids during pregnancy.1,3,8 Live vaccines pose a theoretical risk to the fetus (although this has not been documented or proven) and are thus contraindicated during pregnancy.1,8 These include the live influenza vaccine, MMR (measles, mumps, rubella), varicella, zoster, and BCG (bacille Calmette-Guerin, for tuberculosis).1,3 If a woman receives any of these live vaccines, it is recommended that she wait at least 1 month before becoming pregnant.1,2
Several other immunizations have also not shown harm or risk to the fetus but are generally avoided until after the baby is delivered unless there is a clinical indication for which they should be given. For instance, HPV can wait until after the pregnancy; however, if it is given inadvertently during pregnancy there has not been shown to be any negative effect.1,4 The HPV vaccine should not be delayed if a woman is actively trying to conceive.2 Once pregnant, it is recommended that remaining doses be delayed until after pregnancy.1 The hepatitis B vaccine is also not contraindicated during pregnancy and should be given to women who are high risk if they do not show immunity.1,4 Risk factors include more than one sexual partner during the last 6 months, evaluation or treatment for a sexually transmitted infection during pregnancy, recent injectable drug use, chronic liver disease, HIV, or a sexual partner with hepatitis B.1,4 If a pregnant woman is found to be positive for hepatitis B, the infant should receive the hepatitis B vaccination and HBIg (hepatitis B immune globulin) immediately after birth.1 Similarly, if a woman is exposed to or at high risk for contracting meningitis, the meningococcal vaccine should be given.1,4 If a woman is found not to be immune to rubella, this vaccine should be given after giving birth.1 None of the immunizations are contraindicated for breast-feeding.1
There are several things we can do, as providers, to encourage vaccination during pregnancy to help protect not only the newborn infants, but their mothers as well. By focusing on the safety and effectiveness of the individual vaccines for both mother and baby, instead of the negative effects of declining the vaccines, we can build a positive relationship and reassure families that they are doing what is best for the mother's and baby's health.3 Studies show that receipt of negative information regarding immunizations has more of an impact on vaccine decisions than receipt of positive information, regardless of the source of that information.12 Gaining the trust of our patients could help improve immunization rates and promote the safety of our patients. Educating a patient about vaccination face-to-face during a visit also has a much larger impact than a letter or phone call.3,8 In fact, studies have shown that verbal communication given in person increases vaccine acceptance up to 3 times more than other modes of education.3 Providers should also normalize vaccination as part of routine prenatal care and they should clearly state their support of the recommended vaccinations during pregnancy.3 Lack of this clear recommendation from their provider is a leading predictor of not getting the appropriate maternal vaccinations.3 It is also important to offer the vaccines on-site and during routine visits to provide easy access and convenience for families.3,8
Immunizations are an important part of health throughout life. They are a special consideration for women during pregnancy. Working to improve immunization rates for the Tdap and influenza vaccines during pregnancy, as well as encouraging maintenance of good immunization habits throughout life, will improve the health of our perinatal, postnatal, and neonatal populations. By providing quality information, strong recommendations, and an emphasis on the positive benefits of immunization, we can ensure that pregnant mothers and subsequently their newborn babies are receiving the best possible care.
- Centers for Disease Control and Prevention. Guidelines for vaccinating pregnant women. Updated August 2016. https://www.cdc.gov/vaccines/pregnancy/hcp-toolkit/guidelines.html. Accessed June 12, 2019.
- [No authors listed]. ACOG committee opinion No. 762: prepregnancy counseling. Obstet Gynecol. 2019;133(1):e78–e89. doi:. doi:10.1097/AOG.0000000000003013 [CrossRef]
- Moniz M, Beigi R. Maternal immunization: clinical experiences, challenges, and opportunities in vaccine acceptance. Hum Vaccin Immunother. 2014;10(9):2562–2570. doi:. doi:10.4161/21645515.2014.970901 [CrossRef]
- [No authors listed]. ACOG committee opinion No. 741. Maternal immunization. Obstet Gynecol. 2018;131(6):e214–e217. doi:. doi:10.1097/AOG.0000000000002662 [CrossRef]
- Baxter R, Bartlett J, Fireman B, et al. Effectiveness of vaccination during pregnancy to prevent infant pertussis. Pediatrics. 2017;139(5). pii:e20164091. doi:. doi:10.1542/peds.2016-4091 [CrossRef]
- Centers for Disease Control and Prevention. Tdap (pertussis) vaccine and pregnancy. Updated August 2017. https://www.cdc.gov/vaccines/pregnancy/hcp-toolkit/tdap-vaccine-pregnancy.html. Accessed June 12, 2019.
- Blain A, Lewis M, Banerjee E, et al. An assessment of the cocooning strategy for preventing infant pertussis—United States, 2011. Clin Infect Dis. 2016;63(suppl 4):S221–S226. doi:. doi:10.1093/cid/ciw528 [CrossRef]
- Committee on Obstetric Practice, Immunization and Emerging Infections Expert Work Group. Committee opinion No. 718. update on immunization and pregnancy: tetanus, diphtheria, and pertussis vaccination. Obstet Gynecol. 2017;130(3):e153–e157. doi:. doi:10.1097/AOG.0000000000002301 [CrossRef]
- Munoz F, Bond N, Maccato M, et al. Safety and immunogenicity of tetanus diphtheria and acellular pertussis (Tdap) immunization during pregnancy in mothers and infants: a randomized clinical trial. JAMA. 2014;311(17):1760–1769. doi:. doi:10.1001/jama.2014.3633 [CrossRef]
- Lakshmi S, McCarthy N, Kharbanda E, et al. Safety of tetanus, diphtheria, and acellular pertussis and influenza vaccinations in pregnancy. Obstet Gynecol.2015;126(5):1069–1074. doi:. doi:10.1097/AOG.0000000000001066 [CrossRef]
- Naleway A, Irving S, Henniger M, et al. Safety of influenza vaccination during pregnancy: a review of subsequent maternal obstetric events and findings from two recent cohort studies. Vaccine. 2014;32(26):3122–3127. doi:. doi:10.1016/j.vaccine.2014.04.021 [CrossRef]
- Veerasingam P, Grant CC, Chelimo C, et al. Vaccine education during pregnancy and timeliness of infant immunization. Pediatrics. 2017;140(3). pii: e20163727. doi:. doi:10.1542/peds.2016-3727 [CrossRef]