The new Centers for Disease Control and Prevention immunization schedule, released in late January, recommends that a dose of the Tdap vaccine be administered to all women during each pregnancy, whether or not she has received the vaccine previously (Pediatrics 2013;131:397-404 [doi: 10.1542/peds.2012-3706]). This is a change from the 2011 recommendation that only women who have not had the Tdap vaccine should be vaccinated during pregnancy, preferably during the third or late second trimester. Like the 2011 recommendation, the 2013 recommendation states that a dose of Tdap should be administered immediately after delivery if a woman has not received the vaccine during pregnancy.
This recommendation for a Tdap dose during every pregnancy may initially strike both clinicians and patients as somewhat extreme, but the basis of the new recommendation is quite clear: A huge pertussis epidemic is currently affecting parts of the United States, with more than 41,000 cases reported last year and infants disproportionately affected. Most pertussis deaths and hospitalizations between 2000 and 2012 occurred among children under age 3 months, according to the Centers for Disease Control and Prevention (CDC).
Dr. Gideon Koren
Logically, the CDC’s Advisory Committee for Immunization Practices (ACIP) Pertussis Working Group concluded that one dose during one pregnancy was not sufficient to provide protection during subsequent pregnancies, and revised the recommendation based on considerations that included the continued high number of pertussis cases, evidence that less than 3% of women are getting the vaccine during pregnancy as recommended, and hesitancy of health care providers to vaccinate when a patient’s Tdap vaccine history is not known.
To highlight the importance of this new guideline, the working group described a 40-day-old baby who died from pertussis, whose mother had received a postpartum Tdap dose 2 years earlier but developed a cough illness a week before delivery. A dose of Tdap in the late second or third trimester provides immunity to the mother, with effective antibody response and placental transfer of pertussis antibodies, and is likely to provide passive immunity for infants until the first Tdap dose given to them becomes protective. This is a powerful example of the "cocooning" strategy, whereby the mother is vaccinated to allow protection of the newborn.
Other examples of cocooning include tetanus toxoid vaccination during pregnancy (two doses during the first pregnancy and one dose during other pregnancies), recommended in countries where tetanus is endemic to protect newborns from tetanus; and trivalent influenza vaccine administered during pregnancy.
While both clinicians and parents may be concerned about potential, unknown risks, particularly with repeated vaccination in subsequent pregnancies, the risk of pertussis in the newborn and young infants is by far greater. As painfully demonstrated in the present epidemic, the increased risk of respiratory failure and death associated with pertussis in infants is not theoretical.
To date, there are no data to suggest increased fetal, maternal, or pregnancy risks with exposure to the vaccine. Moreover, the recommendation is that the vaccine be administered in the second or third trimester, after the completion of embryogenesis. In March 2012, the ACOG Committee on Obstetric Practice’s Opinion on Tdap Vaccination stated that "there is no evidence of adverse fetal effects from the vaccination of pregnant women with an inactivated virus, bacterial vaccine, or toxoid, and these should be administered as indicated" (Committee Opinion No. 521. March 2012).
As for the safety of repeated vaccination, there is no biological basis for concern, although no data have yet been collected. The working group described the safety data on two Tdap doses as "reassuring," noting that the tetanus toxoid vaccine has not been associated with an excess risk of adverse events. Recently published studies in nonpregnant adults and adolescents found that a repeat Tdap dose 5 or 10 years after the first dose was well tolerated and immunogenic. In addition, the risk of severe hypersensitivity reactions associated with multiple Tdap doses in pregnancy is "unlikely," based on a recent study of tetanus and diphtheria toxoids (Vaccine 2012;30:974-82; Vaccine 2011;29:8459-65).
In reality, most women are not likely to receive more than two doses, and only about 5% of women would receive four or more doses, based on U.S. data indicating that most women who have children have fewer than three.
The safety of Tdap given during pregnancy should continue to be closely monitored with good pharmacovigilance through the Food and Drug Administration’s Vaccine Safety Datalink and studies evaluating adverse pregnancy and birth outcomes. In Motherisk, we plan to follow up women who receive the Tdap in pregnancy.
In summary, all health care professionals caring for pregnant women should adopt these new guidelines to ensure that the epidemic outbreak of this old disease that kills newborn babies is prevented.