No VAERS safety signal with Tdap in pregnancy

No unexpected adverse events were seen with the administration of Tdap vaccine during pregnancy, although vaccine surveillance data show a shift toward later pregnancy administration.

Serious adverse events, defined as death, life threatening, hospitalization, prolonged hospitalization, and permanent disability, occurred in 6 of 132 (5%) Tdap pregnancies before the recommendation for routine Tdap vaccination during pregnancy and in 14 of 90 (16%) Tdap pregnancies after the recommendation.

The proportion of preterm births (2 vs. 5) and stillbirths (2 vs. 4) increased after the recommendation, while spontaneous abortions decreased (22 vs. 4), Dr. Pedro L. Moro reported at the winter meeting of the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices.

There was one major birth defect before and two after ACIP’s October 2011 recommendation for routine Tdap vaccination during pregnancy.

One of the biggest changes observed in the Vaccine Adverse Event Reporting System (VAERS) reports was the number of women receiving Tdap during the third trimester, up from just 4% to 55% now, said Dr. Moro, an epidemiologist with the CDC.

The most common non–pregnancy-related outcome in the postrecommendation cohort (Oct. 11, 2011-Jan. 31, 2014) was injection site reactions in 19, compared with 6 reported in the prerecommendation cohort (January 2005-June 2010).

"Changes in reporting patterns are likely due to the new routine Tdap recommendation, increased awareness, and differences in the trimester of vaccination," he said.

Pediatric infectious disease specialist and vaccine developer Dr. Stanley Plotkin said he was troubled that 45% of women are still receiving Tdap before the third trimester because this fails to derive maximum benefit from the vaccine in terms of transmitting passive antibodies to the infant.

"It seems to me the recommendation should be stronger for a third-trimester vaccination than for early [vaccination]," he said. "Also, the issue of confusion with congenital anomalies if the vaccine is given in the first trimester, could damage the idea of safety of vaccinations during pregnancy."

The issue of high antibody levels at birth is important, but "We shouldn’t assume that 45% of the Tdap doses are being given before the third trimester because that is not what this VAERS can tell us," commented Dr. Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases.

During his presentation, Dr. Moro emphasized that VAERS looks for safety signals and generates hypotheses, but has inconsistent data quality and completeness and was not designed to assess whether a vaccine caused an adverse event.

Dr. Moro reported having no financial disclosures.

pwendling@frontlinemedcom.com