Impact of a Pertussis Cocooning Program on Infant Pertussis
Impact of a Pertussis Cocooning Program on Infant Pertussis
Background Tetanus, diphtheria and acellular pertussis immunization of infant contacts (cocooning) is recommended by the Centers for Disease Control and Prevention to prevent infant pertussis. We determined whether implementing a cocooning program at Ben Taub General Hospital, Houston, reduced severe pertussis in young infants.
Methods Infants ≤6 months of age, diagnosed with pertussis (determined by International Classification of Diseases, Ninth Revision codes and microbiology records) at 4 hospitals, and born at times when only postpartum women (January 2008 through May 2009) and all infant contacts (June 2009 through August 2011) were offered tetanus, diphtheria and acellular pertussis vaccine at Ben Taub General Hospital were compared with infants born preintervention (May 2004 through December 2007).
Results One hundred ninety-six (49%) infants with pertussis were born preintervention, 140 (35%) during maternal postpartum (PP) and 64 (16%) during cocooning (C) periods. Infants were similar in age at diagnosis (81.2 vs. 71.3 [PP] vs. 72.5 [C] days; P 0.07), sex (male 59% vs. 51% [PP] vs. 48% [C]; P 0.17), hospitalization (68% vs. 71% [PP] vs. 78% [C]; P 0.27) and outcome (2 deaths in the PP period; P 0.15), but more were admitted to intensive care units during cocooning (24% vs. 35% [PP] vs. 68% [C]; P < 0.001). Similar proportions of infants were born at Ben Taub General Hospital throughout the study (8% vs. 9% [PP] vs. 5% [C]; P 0.53).
Conclusions Postpartum immunization and cocooning did not reduce pertussis illness in infants ≤6 months of age. Efforts should be directed toward increasing tetanus, diphtheria and acellular pertussis immunization during pregnancy, combined with cocooning, to reduce life-threatening young infant pertussis.
Considerable advances have been made in reducing the incidence, morbidity and mortality of vaccine-preventable diseases, especially in resource-rich nations. Pertussis is an exception and outbreaks are regularly reported with morbidity and mortality overrepresented in very young infants. Despite high infant immunization rates with diphtheria, tetanus and acellular pertussis (DTaP) vaccine, the United States recorded its highest number of pertussis cases (48,277) in over 50 years in 2012. Infants who are too young to have received their primary immunization series at 2, 4 and 6 months of age consistently have the highest pertussis attack rates and complications. Pertussis-related deaths occur predominantly in infants less than 3 months of age. Reducing pertussis disease burden in young infants has been the objective of pertussis immunization recommendations from the Centers for Disease Control and Prevention (CDC) since the tetanus, diphtheria and acellular pertussis (Tdap) booster vaccine for adolescents and adults was licensed in 2005.
Targeted immunization of postpartum women and contacts of infants under 1 year of age (cocooning) was first recommended in 2006. This recommendation was based on studies demonstrating that most pertussis-infected infants are infected by a household contact (75%), most commonly (33%) their mother, many of whom are unaware that they are infected. Although data were lacking as to the efficacy of this intervention, computer simulation modeling predicted that cocooning could reduce pertussis incidence by 70% in infants less than 3 months of age. Successful cocooning programs in hospital, neonatal intensive care unit and pediatric clinic settings have been reported but logistical and financial barriers precluded widespread implementation of cocooning at a national level. In 2008, a pertussis immunization program was established in a county hospital in Houston, TX. Initially, the program provided free Tdap to postpartum women, and it later expanded to include all household contacts of newborn infants (cocooning). We previously reported that immunizing only postpartum women with Tdap did not reduce pertussis among infants ≤6 months of age. The objective of the current study was to evaluate whether expanding access to free Tdap vaccine to other contacts of young infants reduced severe pertussis in infants in the greater Houston metropolitan area. This study preceded the CDC recommendation to provide Tdap vaccine to pregnant women after week 20 of gestation, and the later recommendation that pregnant women receive Tdap during the third trimester of every pregnancy.
Abstract and Introduction
Abstract
Background Tetanus, diphtheria and acellular pertussis immunization of infant contacts (cocooning) is recommended by the Centers for Disease Control and Prevention to prevent infant pertussis. We determined whether implementing a cocooning program at Ben Taub General Hospital, Houston, reduced severe pertussis in young infants.
Methods Infants ≤6 months of age, diagnosed with pertussis (determined by International Classification of Diseases, Ninth Revision codes and microbiology records) at 4 hospitals, and born at times when only postpartum women (January 2008 through May 2009) and all infant contacts (June 2009 through August 2011) were offered tetanus, diphtheria and acellular pertussis vaccine at Ben Taub General Hospital were compared with infants born preintervention (May 2004 through December 2007).
Results One hundred ninety-six (49%) infants with pertussis were born preintervention, 140 (35%) during maternal postpartum (PP) and 64 (16%) during cocooning (C) periods. Infants were similar in age at diagnosis (81.2 vs. 71.3 [PP] vs. 72.5 [C] days; P 0.07), sex (male 59% vs. 51% [PP] vs. 48% [C]; P 0.17), hospitalization (68% vs. 71% [PP] vs. 78% [C]; P 0.27) and outcome (2 deaths in the PP period; P 0.15), but more were admitted to intensive care units during cocooning (24% vs. 35% [PP] vs. 68% [C]; P < 0.001). Similar proportions of infants were born at Ben Taub General Hospital throughout the study (8% vs. 9% [PP] vs. 5% [C]; P 0.53).
Conclusions Postpartum immunization and cocooning did not reduce pertussis illness in infants ≤6 months of age. Efforts should be directed toward increasing tetanus, diphtheria and acellular pertussis immunization during pregnancy, combined with cocooning, to reduce life-threatening young infant pertussis.
Introduction
Considerable advances have been made in reducing the incidence, morbidity and mortality of vaccine-preventable diseases, especially in resource-rich nations. Pertussis is an exception and outbreaks are regularly reported with morbidity and mortality overrepresented in very young infants. Despite high infant immunization rates with diphtheria, tetanus and acellular pertussis (DTaP) vaccine, the United States recorded its highest number of pertussis cases (48,277) in over 50 years in 2012. Infants who are too young to have received their primary immunization series at 2, 4 and 6 months of age consistently have the highest pertussis attack rates and complications. Pertussis-related deaths occur predominantly in infants less than 3 months of age. Reducing pertussis disease burden in young infants has been the objective of pertussis immunization recommendations from the Centers for Disease Control and Prevention (CDC) since the tetanus, diphtheria and acellular pertussis (Tdap) booster vaccine for adolescents and adults was licensed in 2005.
Targeted immunization of postpartum women and contacts of infants under 1 year of age (cocooning) was first recommended in 2006. This recommendation was based on studies demonstrating that most pertussis-infected infants are infected by a household contact (75%), most commonly (33%) their mother, many of whom are unaware that they are infected. Although data were lacking as to the efficacy of this intervention, computer simulation modeling predicted that cocooning could reduce pertussis incidence by 70% in infants less than 3 months of age. Successful cocooning programs in hospital, neonatal intensive care unit and pediatric clinic settings have been reported but logistical and financial barriers precluded widespread implementation of cocooning at a national level. In 2008, a pertussis immunization program was established in a county hospital in Houston, TX. Initially, the program provided free Tdap to postpartum women, and it later expanded to include all household contacts of newborn infants (cocooning). We previously reported that immunizing only postpartum women with Tdap did not reduce pertussis among infants ≤6 months of age. The objective of the current study was to evaluate whether expanding access to free Tdap vaccine to other contacts of young infants reduced severe pertussis in infants in the greater Houston metropolitan area. This study preceded the CDC recommendation to provide Tdap vaccine to pregnant women after week 20 of gestation, and the later recommendation that pregnant women receive Tdap during the third trimester of every pregnancy.