Pertussis vaccines

Our baby at 19 weeks

I took the day off and went with Holly to see the midwife. Everything looks good! Holly had hoped to know the sex of our baby with today's ultrasound, but the US tech wasn't able to get a good enough picture to tell. We're happy just knowing that our baby looks healthy.

I've spent the last two weeks reading up on pertussis vaccines to prepare for writing this post. I have decided to address adult pertussis immunization and infant pertussis immunization separately.

I almost feel like I should use a "good news-bad news" format for this post. Pertussis vaccines are highly effective but, because immunity to pertussis from either natural infection or vaccination wanes, it is difficult to control the disease.

Prior to the development of pertussis vaccines, there were 115,000 to 270,000 cases of pertussis and 5,000 to 10,000 deaths from pertussis in the U.S. every year. The use of pertussis vaccine in the U.S. has resulted in a 99% reduction in the number of cases of pertussis.

CDC, 2002

Pertussis vaccines are highly effective but, because immunity to pertussis from either natural infection or vaccination only lasts about 10 years, the incidence of pertussis in the U.S. has increased over the last 30 years. California recently had a large pertussis epidemic and, here in Washington State, there is currently an outbreak in Snohomish County.

All pertussis vaccines licensed in the U.S. are combination vaccines with tetanus and diphtheria toxoids (inactivated toxins from the bacteria that cause those diseases). There are two types of pertussis-containing vaccines licensed in the U.S.:

• diphtheria, tetanus, and acellular pertussis (DTaP), which is given to infants and children younger than 7 years of age.
• tetanus, diphtheria, and acellular pertussis (Tdap), which is given to children 7 years of age and older, adolescents, and adults.
• what most people call a "tetanus shot" or "tetanus booster" is actually a tetanus and diphtheria vaccine (Td)

Whole cell pertussis vaccines

Whole cell pertussis vaccines (DTP or DTwP), which are no longer used in the U.S., contained killed Bordetella pertussis bacteria. These vaccines include around 3,000 antigens. These vaccines are highly effective and are still used in some countries, but the high number of antigens in whole cell vaccines increased the risk of side effects.

Acellular pertussis vaccines

Bordetella pertussis produces toxins that allow it to attach to and kill cells in the respiratory tract. Acellular ("without cells") pertussis vaccines contain inactivated pertussis toxins instead of the whole organism. Because these vaccines contain 2 to 5 pertussis antigens, side effects occur much less frequently than with the old whole cell pertussis vaccines.

Cocooning

In the U.S., the majority of cases of pertussis are in babies too young to have received three doses of DTaP (Babies receive DTaP at 2, 4, and 6 months of age. Until then, they are susceptible to pertussis). Over half of these babies get pertussis from one of their parents, most often, from their mother.

To prevent babies from getting pertussis, the American College of Obstetricians and Gynecologists (ACOG) and the CDC's Advisory Committee on Immunization Practices (ACIP) recommend a dose of Tdap after 20 weeks of gestation (late 2^nd trimester or in the 3^rd trimester) for pregnant women who have not previously received a dose of Tdap. This includes women who received DTP or DTaP during childhood.

Both the ACOG and ACIP also recommend a dose of Tdap for everyone who has or anticipates having contact with a baby less than 1 year of age. This includes brothers and sisters, grandparents, and, most importantly, fathers (As a health care provider, I received my Tdap in 2006; before it was recommended for the general population). This strategy is known as "cocooning."

Additional protection

Pertussis antibodies are actively transported across the placenta to the baby in the womb. In fact, the concentration of pertussis antibodies is higher in cord blood than it is in the mother's blood. So, in addition to preventing transmission of pertussis from mother to baby, giving a Tdap to a pregnant woman may also provide the baby with passive immunity to pertussis in its first months of life.

Additional information:

• American Academy of Pediatrics: Pertussis
• American College of Obstetricians and Gynecologists: Immunization for Women
• Centers for Disease Control and Prevention: Pertussis (Whooping Cough) Vaccination
• Immunization Action Coalition: Pertussis (whooping cough)
• National Network for Immunization Information: Pertussis (Whooping Cough)

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. (2002). Pertussis – United States, 1997-2000. Morbidity and Mortality Weekly Report, 51(4), 73-76. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5104a1.htm.

Centers for Disease Control and Prevention. (2011). Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine from the Advisory Committee on Immunization Practices, 2010. Morbidity and Mortality Weekly Report, 60(1), 13-15. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6001a4.htm.

Centers for Disease Control and Prevention. (2011). Updated recommendations for use of tetanus toxoid, reduced diphtheria and acellular pertussis vaccine (Tdap) in pregnant women and persons who have or anticipate having close contact with an infant <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 (5^th Ed.). [Electronic version].

Gall, S. A. (2008). Vaccines for pertussis and influenza: recommendations for use in pregnancy. Clinical Obstetrics and Gynecology, 51(3), 486-497. doi:10.1097/GRF.0b013e318181dde1.

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.

Lavin, J., Broutin, H., Harville, E. T., & Bjørnstad, O. N. (2011). Imperfect vaccine-induced immunity and whooping cough transmission to infants. Vaccine, 29(1), 11-16. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2997163.

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 infant's immune system? Pediatrics, 109(1), 124-129. http://pediatrics.aappublications.org/content/109/1/124.full.

Quinello, C., Quintilio, W., Carneiro-Sampaio, M., & Palmeira, P. (2010). Passive acquisition of protective antibodies reactive with Bordetella pertussis in newborns via placental transfer and breast-feeding. Clinical Immunology, 72(1), 66-73. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3083.2010.02410.x/full.

Wendelboe, A. M., Van Rie, A., Salmaso, S., & Englund, J. A. (2005). Duration of immunity against pertussis after natural infection or vaccination. Pediatric Infectious Disease Journal, 24(5), S58-S61. http://journals.lww.com/pidj/Fulltext/2005/05001/Duration_of_Immunity_Against_Pertussis_After.11.aspx.