The safety of Tdap in pregnancy

The prettiest 20-weeks pregnant
woman I've ever seen!

Holly stopped at a produce stand yesterday to stock up on fruits and vegetables. We're both making an extra effort to eat healthier and take care of ourselves. We're responsible for another person other than ourselves and each other. Of course, we're much more careful about what Holly eats and what she's exposed to.

People are justifiably concerned about the safety of vaccines during pregnancy. In response to my post on tetanus, I received a request to provide studies on the safety of tetanus, diphtheria, and acellular pertussis vaccines (Tdap) during pregnancy.

The data and studies that support the Advisory Committee on Immunization Practice (ACIP) recommendations are found in the recommendations themselves. These are published in the CDC's Morbidity and Mortality Weekly Report (MMWR).

Be forewarned: they're not easy to read.

As I wrote in my response to anonymous, the ACIP recommendations for use of Tdap in pregnant women cited two studies (Gall et al., 2011 and Talbot et al., 2010) that "did not suggest any elevated frequency or unusual patterns of adverse events in pregnant women who received Tdap"

The ACIP examined the safety of Tdap in pregnancy in detail in a previous recommendation.

The safety of tetanus toxoid vaccines in pregnancy was first evaluated in the 1960's and the safety of diphtheria vaccine in pregnancy was evaluated in the 1970's. Since the mid 1970's, the World Health Organization (WHO) Expanded Programme on Immunizations (EPI) has included a recommendation for the use of tetanus toxoid in pregnant women to prevent neonatal tetanus. Since the early 1980's, the CDC and American College of Obstetricians and Gynecologists have recommended tetanus and diphtheria vaccine (Td) for under-immunized pregnant women.

Both tetanus toxoid and diphtheria toxoid vaccines, together and separately, have over 30 years of safe use during pregnancy.

There were several studies of whole cell pertussis vaccines in pregnancy in the 1930's and 1940's. No serious adverse reactions in either mother or baby were recorded. Remember that whole-cell pertussis vaccines have around 3,000 antigens compared to the Tdap vaccines currently licensed in the U.S. which contain only three or five inactivated pertussis toxins.

In their General recommendations on immunization, the ACIP states, "Risk to a developing fetus from vaccination of the mother during pregnancy is theoretical. No evidence exists of risk to the fetus from vaccinating pregnant women with inactivated virus or bacterial vaccines or toxoids." The American College of Obstetricians and Gynecologists echoes that statement in their Update of immunization and pregnancy: Tdap.

ACOG also states, "Ideally, vaccines should be administered before conception." For reasons other than concern about the safety of the vaccine during pregnancy, Holly received her Tdap in 2008.

Additional information:

• Centers for Disease Control and Prevention: Guidelines for Vaccinating Pregnant Women
• Immunization Action Coalition: Tetanus Vaccine Questions and Answers
• National Network for Immunization Information: Vaccines for Pregnant Women

References

American College of Obstetricians and Gynecologists. (2012). Update on immunization and pregnancy: tetanus, diphtheria, and pertussis vaccination. Obstetrics and Gynecology, 119(3), 690-691. http://www.acog.org/Resources_And_Publications/Committee_Opinions/Committee_on_Obstetric_Practice/Update_on_Immunization_and_Pregnancy_Tetanus_Diphtheria_and_Pertussis_Vaccination.

Centers for Disease Control and Prevention. (1983). Recommendations of the Immunization Practices Advisory Committee general recommendations on immunizations. Morbidity and Mortality Weekly Report, 32(1), 13-17. http://www.cdc.gov/mmwr/preview/mmwrhtml/00001226.htm.

Centers for Disease Control and Prevention. (2008). Prevention of pertussis tetanus, and diphtheria among pregnant and postpartum women and their infants. Morbidity and Mortality Weekly Report, 57(4), 1-47, 51. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5704a1.htm.

Centers for Disease Control and Prevention (2011). General recommendations on immunizations. Recommendations of the Advisory Committee on Immunization Practices (ACIP). Morbidity and Mortality Weekly Report, 60(2), 1-60. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6002a1.htm.

Centers for Disease Control and Prevention. (2011). Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine (Tdap) in pregnant women and persons who have or anticipate having close contact with an infant aged <12 months – Advisory Committee on Immunization Practices (ACIP), 2011. Morbidity and Mortality Weekly Report, 60(41), 1424-1426. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6041a4.htm.

Edwards, K. M. & Decker, M. D. (2008) Pertussis vaccines. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds.) Vaccines (5th Ed.). [Electronic version].

Gall, S. A., Myers, J., & Pichichero, M. (2011). Maternal immunization with tetanus-diphtheria-pertussis vaccine: effect on maternal and neonatal serum antibody levels. American Journal of Obstetrics & Gynecology, 204(4), 334.e1-5. doi.org/10.1016/j.ajog.2010.11.024.

Offit, P. A., Quarles, J., Gerber, M. A., Hackett, C. J., Marcuse, E. K., Kollman, T. R. et al. (2002). Addressing parents’ concerns: do multiple vaccines overwhelm or weaken the infants immune system? Pediatrics, 109(1), 124-129. http://pediatrics.aappublications.org/content/109/1/124.full.

Talbot, E. A., Brown, K. H., Kirkland, K. B., Baughman, A. L., Halperin, S. A., & Broder, K. R. (2010). The safety of immunizing with tetanus-diphtheria-acellular pertussis vaccine (Tdap) less than 2 years following a previous tetanus vaccination: experience during a mass vaccination campaign of healthcare personnel during a respiratory illness outbreak. Vaccine, 28(50), 8001-8007. doi:10.1016/j.vaccine.2010.09.034.

Wassilak, S. G. F., Roper, M. H., Kretsinger, K., Orenstein, W. A. (2008). Tetanus toxoid. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds) Vaccines (5th Ed.). [Electronic version].