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Tdap vaccination during pregnancy

The majority cases of pertussis (whooping cough) in the U.S. occur in susceptible infants under 3 months of age. Vaccination against pertussis is safe and indicated during every pregnancy, at 27–36 weeks’ gestation, and protects both the woman and her newborn. 

Diagnosis/definition: Pertussis is a respiratory bacterial infection, typically associated with paroxysmal coughing that may continue for weeks. Potential complications in infants with pertussis include apnea, pneumonia, encephalopathy, and death. The majority of pertussis cases reported in the United States, specifically hospitalizations and deaths related to this infection, occur in infants aged <3 months, who are below the 2-month-old age limit for pertussis vaccination under current national guidelines.

Epidemiology/Incidence: Since 2004, an average annual rate of approximately 3000 infant pertussis cases per year, with more than 19 deaths per year, has been reported to the National Notifiable Diseases Surveillance System, with significant outbreaks initially reported in California and Washington State.
Risk factors/associations: The majority of newborns who contract pertussis acquire the disease from immediate family members, including their mothers. Vaccination against pertussis in family members and other caregivers of newborns is a primary strategy to provide protection in this vulnerable period.

Complications: Tdap is an inactivated vaccine and safe during pregnancy. The pertussis antigen component is purified from the B. pertussis bacterium and then inactivated. There are no live bacteria in the vaccine, and it cannot cause pertussis in a vaccinated child or adult. Prevention: Maternal immunization against pertussis during pregnancy allows transplacental passage of maternal antibodies to the fetus, providing neonatal coverage until the infancy vaccine series against pertussis can begin. These specific antibodies confer protection and modify the severity of pertussis in infants. 

Prenatal Management: Antibody levels after Tdap vaccination peak after several weeks, followed by a decline over several months. Vaccination is suggested during the third trimester, ideally close to 30 weeks’ gestation (preferably during weeks 27–36), when active transport of antibodies becomes most efficient. Vaccination later in the third trimester may not allow the minimum of 2 weeks that is required to mount a maximal antibody response. In addition, because of the waning of maternal antibody levels after pregnancy, revaccination with Tdap for neonatal benefit is now recommended with every pregnancy.