The Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention is taking measures to fill a gap in the protection of infants from pertussis, by vaccinating pregnant women and people in contact with infants younger than 1 year.
The tetanus, diphtheria, and pertussis (Tdap) vaccine consists of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine. Vaccinating pregnant women and those in contact with infants will supplement the current practice of “cocooning,” in which unvaccinated postpartum mothers and other family members receive Tdap. Although ACIP has recommended cocooning since 2005, compliance has been poor. ACIP also recommends Tdap for people aged 11 through 18 years after they complete the childhood vaccine regimen of diphtheria and tetanus toxoids and pertussis/diphtheria and tetanus toxoids and acellular pertussis, as well as for adults between the ages of 19 and 64 years who have not received Tdap, in addition to people older than 65 years who may be in contact with infants who have not received the vaccine.
The reason for the new recommendations is that infants, especially those younger than 2 months, which is when vaccination begins, are particularly vulnerable to developing severe illness and death from pertussis. Vaccinating pregnant women will pass antibodies to the newborn before and during birth. ACIP advises administration after 20 weeks’ gestation to minimize the confounding effects of early pregnancy loss in evaluating safety and to maximize the maternal antibodies transmitted to the fetus and infant, given that the half-life of such antibodies is 6 weeks. This new perinatal exposure should provide protection until the infant’s first vaccination at 2 months.
In the United States each year since 2004, a mean of 3055 infants contract pertussis, with 19 or more deaths, according to the National Notifiable Diseases Surveillance System of the US Centers for Disease Control and Prevention. The total number of cases reported for 2010 was 27,550.
Abundant evidence indicates that tetanus and diphtheria vaccines are safe during pregnancy. Although the possible teratogenicity of the vaccine was not initially studied, data from patient registries maintained by the vaccine manufacturers (Sanofi Pasteur and GlaxoSmithKline Biologicals) indicate that Tdap is safe.
Further studies will investigate whether exposure to maternal antibodies is indeed protective, or whether it blunts the infant’s vaccine response.
The authors have disclosed no relevant financial relationships.
MMWR Morb Mortal Wkly Rep. 2011;60:1424-1426. Full text
— Ricki Lewis, PhD