CDC Panel Expands Tdap Vaccine in Pregnancy Recommendation

Diana Mahoney

October 24, 2012

The Centers for Disease Control and Prevention's (CDC's) Advisory Committee on Immunization Practices (ACIP) voted today to expand the recommendation for the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine during pregnancy to encompass all pregnant women regardless of vaccination history, including repeat vaccinations in subsequent pregnancies.

Before today's vote, the 2011 ACIP recommendations for Tdap in pregnancy specifically targeted previously unvaccinated pregnant women, advising vaccination in this population after 20 weeks' gestation in an effort to reduce the burden of pertussis in infants, as previously reported by Medscape Medical News.

"At the time of the 2011 recommendations, we were already being asked about subsequent pregnancies in previously vaccinated women," according to Jennifer Liang, MD, from the CDC National Center for Immunization and Respiratory Diseases, who presented the proposed changes during the ACIP meeting in Atlanta, Georgia.

The rationale for considering expansion of the recommendation was to improve uptake of Tdap in pregnancy, which is currently only 2.6%, and by so doing reduce the morbidity and mortality associated with pertussis in infants younger than 2 months. "The more universal recommendation for pregnant women would remove real and/or perceived barriers to vaccination," she said.

On the basis of a review of published and unpublished studies on the use of Tdap in pregnant women and Tdap safety data from pregnancy registries and the Vaccine Adverse Event Reporting System, the ACIP Pertussis Vaccine Work Group concluded that "a single dose of Tdap at one pregnancy was insufficient to provide protection for subsequent pregnancies and that the benefits of vaccination outweigh the theoretical risks of severe adverse events," Dr. Liang explained.

In fact, she noted, "although there are no data to address what we really want to know [the potential for severe adverse events associated with repeat vaccinations for pregnant women who have multiple pregnancies in a short time interval], the data from studies in which healthy adults received 2 doses of Tdap are reassuring, and the historical experience with tetanus toxoid vaccine suggests no excess risk of adverse events with multiple doses."

Because Tdap maternal pertussis antibodies appear to wane greatly between subsequent pregnancies, and most women, based on US birth records, are not pregnant more than 2 or 3 times, "a small proportion of women would receive 2 or 3 Tdap doses," according to Dr. Liang.

Although the lack of definitive safety data for those who do receive multiple doses "is not a reason to deter making a recommendation for all pregnancy or for limiting the number of doses," the work group supports ongoing safety monitoring and requests that the CDC commit to safety studies to address concerns about the administration of Tdap during subsequent pregnancies.

By a vote of 14 to 0, with 1 abstention, the ACIP approved the work group's proposed recommendations: that providers of prenatal care implement a Tdap immunization program for all pregnant women and that healthcare personnel administer a dose of Tdap during each pregnancy, regardless of the patient's Tdap history.

As with the 2011 recommendation, the revised guideline recommends immediate postpartum administration of Tdap for women who do not receive it during pregnancy.

According to the work group proposal, language on the timing of the dose (specifically, that the optimal timing for Tdap administration is between 27 and 36 weeks' gestation to maximize maternal antibody response and passive antibody transfer to the infant) will be moved to the guidance section of the recommendation.

The ACIP also voted to include the revised recommendation in the Vaccines for Children Program, so that pregnant adolescents would receive Tdap in the same manner as pregnant adult women.

On acceptance by the director of the CDC and the secretary of the US Department of Health and Human Services, the revised recommendations will be published in the CDC's Morbidity and Mortality Weekly Report in early 2013, according to Mark Sawyer, MD, chair of the ACIP Pertussis Vaccine Working Group.

Dr. Liang and Dr. Sawyer have disclosed no relevant financial relationships.