The use of biologic therapy during pregnancy did not lower antibody titers among infants vaccinated against Haemophilus influenzae B (HiB) or tetanus toxin, according to the results of a study of 179 mothers reported in the January issue of Clinical Gastroenterology and Hepatology (2017. doi: 10.1016/j.cgh.2017.08.041 ).

Additionally, there was no link between median infliximab concentration in uterine cord blood and antibody titers among infants aged 7 months and older, wrote Dawn B. Beaulieu, MD , with her associates. “In a limited cohort of exposed infants given the rotavirus vaccine, there was no association with significant adverse reactions,” they also reported.

Active inflammatory bowel disease (IBD) increases the risk of adverse pregnancy outcomes. Retrospective studies have found no link between anti–tumor necrosis factor therapy and adverse birth outcomes or congenital malformations, but some biologics can cross the placenta and remain in infants for up to a year after birth, the researchers noted. In 2010, an infant whose mother was on infliximab for Crohn’s disease died ( J Crohns Colitis. 2010 Nov;4[5]:603-5 ) after receiving the BCG vaccine, which is contraindicated in individuals on immunosuppressives.

Experts now recommend against live vaccinations for infants who may have detectable concentrations of biologics, but it remained unclear whether these infants can mount adequate responses to inactive vaccines. Therefore, the researchers analyzed data from the Pregnancy in IBD and Neonatal Outcomes ( PIANO ) registry collected between 2007 and 2016 and surveyed women about their infants’ vaccination history. They also quantified antibodies in serum samples from infants aged 7 months and older and analyzed measured concentrations of biologics in cord blood.

Among 179 mothers with IBD, most had inactive (77%) or mild disease activity (18%) during pregnancy, the researchers said. Eleven (6%) mothers were not on immunosuppressives while pregnant, 15 (8%) were on an immunomodulator, and the rest were on biologic monotherapy (65%) or a biologic plus an immunomodulator (21%). A total of 46 infants had available HiB titer data, of whom 38 were potentially exposed to biologics; among 49 infants with available tetanus titers, 41 were potentially exposed. In all, 71% of exposed infants had protective levels of antibodies against HiB, and 80% had protective titers to tetanus toxoid. Proportions among unexposed infants were 50% and 75%, respectively. Proportions of protective antibody titers did not significantly differ between groups even after excluding infants whose mothers received certolizumab pegol, which has negligible rates of placental transfer.

A total of 39 infants received live rotavirus vaccine despite having detectable levels of biologics in cord blood at birth. Seven developed mild vaccine reactions consisting of fever (six infants) or diarrhea (one infant). This proportion (18%) resembles that from a large study ( N Engl J Med. 2006;354:23-33 ) of healthy infants who were vaccinated against rotavirus, the researchers noted. “Despite our data suggesting a lack of severe side effects with the rotavirus vaccine in these infants, in the absence of robust evidence, one should continue to avoid live vaccines in infants born to mothers on biologic therapy (excluding certolizumab) during the first year of life or until drug clearance is confirmed,” they suggested. “With the growing availability of tests, one conceivably could test serum drug concentration in infants, and, if undetectable, consider live vaccination at that time, if appropriate for the vaccine, particularly in infants most likely to benefit from such vaccines.”

The Crohn’s and Colitis Foundation provided funding. Dr. Beaulieu disclosed a consulting relationship with AbbVie, and four coinvestigators also reported ties to pharmaceutical companies.