Pertussis is a continuing threat to Californians, though the magnitude of the threat varies by year as the number of susceptible people in the population waxes and wanes. More than 9,100 cases of pertussis were reported in California during 2010, the most in more than a half-century. Consistent with historical cycles of three to five years between years of higher incidence, cases are likely to increase between 2013 and 2015 in comparison to 2011 and 2012.
Young infants at highest risk of severe pertussis
Infants younger than two months are most susceptible to hospitalization or death from pertussis, but immunization against pertussis is not recommended until at least six weeks of age. However, infants can be protected by maternal antibodies that are transferred through the placenta. Early evidence suggests that vaccinating pregnant women with Tdap during the third trimester of pregnancy can prevent pertussis in young infants.
Optimal timing of maternal Tdap administration
To maximize protection of young infants, the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices (ACIP) recommends that all women be given Tdap during every pregnancy, regardless of previous Tdap status, preferably between 27 and 36 weeks’ gestation. This recommendation is based on the following information:
- Women immunized with Tdap during a prior pregnancy or during the first or second trimester of a current pregnancy appear to have low levels of pertussis antibodies at delivery
- Transplacental transport of antibodies occurs mainly after 30 weeks’ gestation
- At least two weeks are needed for a maximal response to immunization
If Tdap is not administered during pregnancy, it should be given immediately postpartum. This vaccination will not provide direct protection to the infant, but it may prevent transmission of pertussis from mother to infant.
Other close contacts
Everyone (eg, parents, siblings, grandparents, child care providers, and health care personnel) who anticipates close contact with an infant younger than 12 months should receive Tdap if they have not already done so. ACIP is currently considering whether Tdap boosters are indicated for contacts of infants.
“Update on Immunization and Pregnancy: Tetanus, Diphtheria, and Pertussis Vaccination,” ACOG Committee Opinion #566, June 2013
ACIP Updated Recommendations for Use of Tdap in Pregnant Women
California Department of Public Health pertussis summary reports
“Importance of timing of maternal Tdap immunization and protection of young infants,” Clinical Infectious Diseases, February 15, 2013
Pertussis information for Ob-Gyns