Protecting Infants From Pertussis: Are We Making Progress?
Skoff TH, Cohn AC, Clark TA, Messonnier NE, Martin SW
Arch Pediatr Adolesc Med. 2012;166:344-349
Morbidity and mortality due to pertussis are highest among infants. Waning immunity and the lack of classic pertussis symptoms in adolescents and adults mean that they are at risk for unrecognized infection and may serve as reservoirs of pertussis, potentially putting infants and young children at risk.
The current pertussis booster vaccines, which include the reduced dose of the acellular pertussis component along with tetanus and diphtheria (Tdap), were licensed in 2005 and were recommended for routine use for patients aged 11-18 years in 2006. The current emphasis is on providing 1 dose of Tdap booster to patients aged 11-12 years.
The recommendations in 2006 were also for adults 19-64 years old to receive a single dose of Tdap instead of a tetanus booster. Because coverage for Tdap among adolescents 13-17 years is now above 50%, less than 10% of patients aged 19 years or older have received at least 1 dose of Tdap.
Skoff and colleagues' report reviews 20 years of surveillance data to evaluate trends in pertussis in both the overall population and in infants, comparing those trends before and after the introduction of the Tdap booster vaccines in 2005. The investigators divided patients into the following age groups: infancy (< 1 year), 1 to 10 years, 11 to 18 years, and 19 years and older. They calculated incidence rates and rate ratios for pertussis. In general, they considered 1992-2004 to be the pre-booster vaccine period and 2005-2009 to be the post-booster vaccine period.
During 1992-2009, more than 200,000 pertussis cases occurred in the United States, and 66.5% of those cases were confirmed by laboratory methods. An additional 26.7% of cases were considered "probable," because they occurred after known exposures or met appropriate clinical definitions of pertussis.
Overall, the incidence of pertussis increased from 1992 to 2003 across all age groups, peaking nationally in 2004-2005. The incidence declined from 2005 to 2007, consistent with the cyclic nature of pertussis, only to rise again in 2007-2009. Infants had the highest incidence across the entire study period.
Introduction of Tdap was associated with a significant reduction in the incidence of pertussis in patients aged 11-18 years, the group targeted for immunization. In fact, this age group is the only group that experienced a sustained reduction in pertussis incidence on the basis of rate ratios since the introduction of the vaccine.
Skoff and colleagues concluded that the introduction of a booster dose of Tdap met the primary goal of reducing pertussis morbidity among children 11-18 years of age. It does not seem to have affected the incidence in other populations, especially infants.
This study explains some of the reasons why we have not seen a change in the incidence of infant pertussis with the increased use of Tdap booster vaccination among adolescents. First, the rate of Tdap receipt among adolescents barely exceeds 50%. Perhaps of greater importance, adults aged 19 years or older rarely receive the vaccine, so most adults who are caring for infants are not protected. Current efforts to vaccinate pregnant women and focus on household contacts of infants may be a more effective method to secondarily protect infants, and those efforts are actively under way.
This study is very good news for adolescents in that the morbidity they experience from pertussis has diminished, but we still have a long way to go from a vaccination standpoint to better protect other segments of the population.
Abstract
Early Impact of the US Tdap Vaccination Program on Pertussis Trends
Skoff TH, Cohn AC, Clark TA, Messonnier NE, Martin SW
Arch Pediatr Adolesc Med. 2012;166:344-349
Study Summary
Morbidity and mortality due to pertussis are highest among infants. Waning immunity and the lack of classic pertussis symptoms in adolescents and adults mean that they are at risk for unrecognized infection and may serve as reservoirs of pertussis, potentially putting infants and young children at risk.
The current pertussis booster vaccines, which include the reduced dose of the acellular pertussis component along with tetanus and diphtheria (Tdap), were licensed in 2005 and were recommended for routine use for patients aged 11-18 years in 2006. The current emphasis is on providing 1 dose of Tdap booster to patients aged 11-12 years.
The recommendations in 2006 were also for adults 19-64 years old to receive a single dose of Tdap instead of a tetanus booster. Because coverage for Tdap among adolescents 13-17 years is now above 50%, less than 10% of patients aged 19 years or older have received at least 1 dose of Tdap.
Skoff and colleagues' report reviews 20 years of surveillance data to evaluate trends in pertussis in both the overall population and in infants, comparing those trends before and after the introduction of the Tdap booster vaccines in 2005. The investigators divided patients into the following age groups: infancy (< 1 year), 1 to 10 years, 11 to 18 years, and 19 years and older. They calculated incidence rates and rate ratios for pertussis. In general, they considered 1992-2004 to be the pre-booster vaccine period and 2005-2009 to be the post-booster vaccine period.
During 1992-2009, more than 200,000 pertussis cases occurred in the United States, and 66.5% of those cases were confirmed by laboratory methods. An additional 26.7% of cases were considered "probable," because they occurred after known exposures or met appropriate clinical definitions of pertussis.
Overall, the incidence of pertussis increased from 1992 to 2003 across all age groups, peaking nationally in 2004-2005. The incidence declined from 2005 to 2007, consistent with the cyclic nature of pertussis, only to rise again in 2007-2009. Infants had the highest incidence across the entire study period.
Introduction of Tdap was associated with a significant reduction in the incidence of pertussis in patients aged 11-18 years, the group targeted for immunization. In fact, this age group is the only group that experienced a sustained reduction in pertussis incidence on the basis of rate ratios since the introduction of the vaccine.
Skoff and colleagues concluded that the introduction of a booster dose of Tdap met the primary goal of reducing pertussis morbidity among children 11-18 years of age. It does not seem to have affected the incidence in other populations, especially infants.
Viewpoint
This study explains some of the reasons why we have not seen a change in the incidence of infant pertussis with the increased use of Tdap booster vaccination among adolescents. First, the rate of Tdap receipt among adolescents barely exceeds 50%. Perhaps of greater importance, adults aged 19 years or older rarely receive the vaccine, so most adults who are caring for infants are not protected. Current efforts to vaccinate pregnant women and focus on household contacts of infants may be a more effective method to secondarily protect infants, and those efforts are actively under way.
This study is very good news for adolescents in that the morbidity they experience from pertussis has diminished, but we still have a long way to go from a vaccination standpoint to better protect other segments of the population.
Abstract
Source...