Receiving the tetanus, diphtheria, acellular pertussis vaccine during pregnancy does not increase the risk of adverse events for mother or baby, even if the mother has previously received the vaccine within the past 2 years, according to a report published Oct. 20 in JAMA.
Women should receive a Tdap vaccination during each pregnancy – preferably in the third trimester – so that the fetus receives some maternal antibodies against pertussis for limited protection until the first DTaP vaccine at age 2 months, according to 2012 recommendation from the Advisory Committee on Immunization Practices (ACIP). Yet previous research has not clarified the safety of repeated doses of maternal Tdap immunization.
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“These findings suggest that relatively recent receipt of a prior tetanus-containing vaccination does not increase risk after Tdap vaccination in pregnancy,” wrote Dr. Lakshmi Sukumaran of the Centers for Disease Control and Prevention Immunization Safety Office, and colleagues. “Our findings should reassure patients and clinicians who might be hesitant to give Tdap vaccine to pregnant women who recently received a Tdap or other tetanus-containing vaccination.”
In the retrospective cohort study involving pregnancies between Jan. 1, 2007, through Nov. 15, 2013, the researchers examined data from 29,155 pregnant women, aged 14-49, who enrolled in seven Vaccine Safety Datalink sites in California, Colorado, Minnesota, Oregon, Washington, and Wisconsin.
The researchers compared the 49% of women who had received a tetanus-containing vaccine more than 5 years before their current pregnancy (controls) with the 17% of women who had received a tetanus-containing vaccine less than 2 years before, and the 34% of women who had been vaccinated 2-5 years earlier. More than two-thirds of the women (67.4%) received the Tdap during the third trimester, compared with 27.5% in the second trimester, and 5.1% in the first trimester (JAMA. 2015;314[15]:1581-7. doi: 10.1001/jama.2015.12790).
The researchers evaluated several adverse events including fever, allergy, and local reactions in mothers in the week following immunization, as well as preterm birth, low birth weight and small for gestational age in newborns. Local reactions included limb pain, limb swelling, cellulitis, lymphadenitis, and Arthus reaction. The researchers also looked for Guillain-Barré syndrome through day 42 after vaccination.
Few acute adverse events occurred after vaccination, and no statistically significant differences occurred across the three groups in terms of fever, allergic reactions, and local reactions.
Women who had received a tetanus-containing vaccine less than 2 years earlier had fevers at a rate of 2.1 per 10,000 women, compared with 3.5 per 10,000 women among controls (adjusted relative rate: 0.66; P = .70). Similarly, allergic reactions occurred at a rate of 2.1 per 10,000 women for those who had a vaccine less than 2 years prior, compared to 1 per 10,000 women who had the vaccine 2-5 years earlier, and 1.4 per 10,000 women among controls.
Local reactions occurred at a rate of 4.2, 7.0 and 11.2 per 10,000 women for those who had the vaccine less than 2 years prior, between 2-5 years prior, and more than 5 years prior, respectively. Preterm delivery rates, low birth weight, and small for gestation age were all similar across the three groups.
The Centers for Disease Control and Prevention and the National Institute of Allergy and Infectious Diseases funded the study. Dr. Sukumaran reported receiving research support from the National Institutes of Health. The other researchers reported receiving research support from GlaxoSmithKline, Sanofi Pasteur, Merck, Pfizer, Nuron Biotech, MedImmune, Novartis, and Protein Science.