How can we best prevent pertussis in infants?

Pertussis is a very contagious respiratory infection, and despite a high rate of vaccine coverage, it is the only vaccinepreventable disease currently increasing in the United States. In 2009 a total of 16 858 cases of pertussis with 12 infant deaths were reported by the Centers for Disease Control and Prevention [1], and 10 infant deaths were also documented in a recent outbreak of pertussis in California [2, 3]. Because infants represent the most severely affected age group, particularly infants ,2 months of age who are too young to have received vaccine, innovative immunization strategies are needed to protect this vulnerable population. Several strategies, including vaccination of newborns, older adolescents and adults, and pregnant women, have been proposed to decrease the rate of pertussis in very young children. One of these strategies, the ‘‘cocoon strategy,’’ seeks to protect newborn infants from subsequent pertussis exposure by administering tetanus and diphtheria toxoids and acellular pertussis (Tdap) vaccine to mothers and other close household contacts before postpartum hospital discharge. Earlier reports demonstrated that nearly 75% of pertussis cases in young infants resulted from exposure to an asymptomatic or mildly symptomatic household member, with the mother identified as the source of the infection in 33% of the cases [4, 5]. Thus, it was postulated that cocooning could protect the infant from household contagion in up to 75% of cases. Computer simulations were used to test the potential impact of 6 immunization strategies on the burden of pertussis in young infants [6]. These strategies included (1) routine childhood diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccinations at 2, 4, and 6 months of age, with boosters at 12–15 months and 4–6 years of age; (2) routine childhood DTaP vaccinations and routine Tdap immunization of adolescents at 12 years of age; (3) routine childhood DTaP and routine Tdap immunization of adolescents and adults at 10-year intervals; (4) routine childhood DTaP and cocooning of infants by immunization of household contacts; (5) routine childhood DTaP vaccinations, routine Tdap immunization of adolescents at 12 years of age, and cocooning; and (6) routine childhood DTaP, routine Tdap immunization of adolescents and adults at 10-year intervals, and cocooning. The simulations showed that the incidence of typical pertussis in young children (0–23 months of age) decreased with all 5 new strategies, but significant reductions in disease rates in very young children (,3 months of age) were projected only with the cocoon strategy. On the basis of these simulations and the need for disease prevention in the youngest children, the Centers for Disease Control and Prevention recommended universal ‘‘cocooning’’ in 2006 [7]. In this issue of the journal, Castagnini and colleagues [8] studied the impact of maternal postpartum Tdap immunization, ‘‘cocooning,’’ on infant pertussis infection. The cocooning intervention took place at 1 hospital, the Ben Taub General Hospital (BTGH) in Houston, Texas, with a predominantly Hispanic, largely medically underserved population. An active educational effort at BTGH informed the pregnant women about the program and provided vaccine at no charge to the patient. During the intervention period, 67% of postpartum women at BTGH received Tdap vaccine. Most women not receiving vaccine had been recently immunized with tetanuscontaining vaccines or had contraindications to vaccination. To measure the impact of the cocooning strategy, the authors conducted a cross-sectional study in 4 Houston hospitals and evaluated the number of laboratory-confirmed pertussis cases in children ,6 months of age before (July 2000 through December 2007) and after the cocooning strategy (January 2008 through May 2009). Cases of pertussis Received 12 September 2011; accepted 23 September 2011; electronically published 10 November 2011. Correspondence: KathrynM. Edwards,MD, Sarah H. Sell and Cornelius Vanderbilt Professor of Pediatrics, CCC 5311 MCN, 1161 21st Ave S, Nashville, TN 37232 (kathryn.edwards@ vanderbilt.edu). Clinical Infectious Diseases 2012;54(1):85–7 The Author 2011. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. [email protected]. DOI: 10.1093/cid/cir780