Tdap during pregnancy did not increase adverse events for mother or child

The risk of adverse events for mother and child were not increased when the mother was given the tetanus-diphtheria-acellular pertussis vaccine during the third trimester of pregnancy, according to recent study findings published in a special theme issue of JAMA.

The issue on Child Health, was released in conjunction with the 2014 Pediatric Academic Societies Annual Meeting.

Flor M. Munoz, MD, of the Baylor College of Medicine, and colleagues randomized 48 healthy pregnant women to receive either Tdap vaccine (n=33) or placebo (n=15) at 30 to 32 weeks’ gestation and evaluated the safety and immunogenicity of the vaccine. The placebo recipients were given Tdap postpartum and Tdap recipients were given placebo postpartum. Thirty-two healthy non-pregnant women were also enrolled in the study.

Flor M. Munoz

Injection site reactions followed Tdap immunization were not different between pregnant participants (78.8%), postpartum participants (80%), and nonpregnant participants (78.1%; P>.99).

The most common reaction among all participants was pain at the injection site (75.8% for pregnant participants; 73.3% for postpartum participants; 78.1% for nonpregnant participants). Symptoms that were infrequent were swelling and erythema. Participants who received Tdap postpartum were more likely to have systemic symptoms (73.3%) compared with those immunized during pregnancy (36.4%) and nonpregnant participants (53.1%). Among all three groups, headache, myalgia, and malaise were not significantly different (P≥.35). However, headache was more common than myalgia and malaise.

Postpartum participants were more likely to experience fever after receiving Tdap (26.7%) compared with pregnant participants (3%) and nonpregnant participants (9.4%).

Twenty-two women reported serious adverse events, including seven who received Tdap during pregnancy and six of their infants; two participants who received Tdap postpartum and six of their infants; and one nonpregnant participant. However, none were thought to be caused by Tdap vaccine. All reported nonserious adverse events occurred without sequelae.

All pregnancies resulted in live births by vaginal delivery and infants were mostly at term. No cases of pertussis occurred among infants or mothers.

Nonpregnant participants and participants vaccinated postpartum did not have different antibody responses compared with participants vaccinated during pregnancy. However, participants vaccinated during pregnancy had higher antibody concentrations to all vaccine antigens at delivery compared with participants vaccinated postpartum. Pertussis antibodies at birth and aged 2 months were higher among infants born to participants vaccinated during pregnancy when compared with other infants whose mothers received placebo during pregnancy.

Natalia Jiménez-Truque

“Tdap immunization during pregnancy was found to be safe for pregnant mothers and their infants, and resulted in high concentrations of antibodies to pertussis which could protect infants in the first few months of life, the period of greatest risk for pertussis complications and mortality,” Munoz told Infectious Diseases in Children.

In an accompanying editorial, Natalia Jiménez-Truque, MSCI, PhD, and Infectious Diseases in Children Editorial Board member Kathryn M. Edwards, MD, of Vanderbilt University Medical Center, wrote that further studies are needed to assess the safety and immunogenicity of Tdap immunization during pregnancy.

Kathryn M. Edwards

“Continued reporting of pertussis cases will also be necessary to assess the effectiveness of administering Tdap during pregnancy,” they wrote. “In addition, the assessment of potential interference with DTaP and other vaccine antigens administered during infancy will require large prospective studies. Last, future research must address the safety and immunogenicity of repeated doses of Tdap during each pregnancy, because frequent immunization might lead to a blunted antibody response.”

Flor M. Munoz, MD, can be reached at One Baylor Plaza, BCM-280, Houston, TX 77030; email: florm@bcm.edu.

Kathryn M. Edwards, MD, can be reached at 2323 MCN, Vanderbilt University, Nashville, TN 37232.

For more information:

Munoz FM. JAMA. 2014;doi:10.1001/jama.2014.3633.

Jiménez-Truque N. JAMA. 2014;doi:10.1001/jama.2014.3555.

Disclosure: See the studies for a full list of researchers’ financial disclosures.