Elimination of Racial Differences in Invasive Pneumococcal Disease in Young Children after Introduction of the Conjugate Pneumococcal Vaccine. Talbot TR, Poehling KA, Hartert TV, Arbogast PG, Halasa NB, Mitchel E, Schaffner W, Craig AS, Edwards KM, and Griffin MR. Pediatric Infectious Disease Journal 2004;23(8):726-731.
Explanatory note: In the past, the incidence of invasive pneumococcal disease has been higher among blacks than among whites in the United States. However, isolates of S. pneumoniae which are not susceptible to traditionally used antibiotics have been recovered more frequently from whites than blacks. Since October 2000, when a 7-valent pneumococcal conjugate vaccine (PCV7) became available for young children, the number of new cases of serious pneumococcal disease in young children has declined dramatically.
What has been the effect of PCV7 introduction on the racial differences in invasive pneumococcal disease in Tennessee?
In this study, researchers analyzed data from an active surveillance system to detect specific infectious diseases including invasive pneumococcal disease (IPD) occurring is 5 urban counties in Tennessee—accounting for 40% of the state’s population.
They identified cases of IPD during the period from 1995 to 2002. Cases were defined as the isolation of S. pneumoniae from a normally sterile body site. Available pneumococcal isolates were subsequently tested for susceptibility to antibiotics and as to whether or not they were related to one of the serotypes contained in the vaccine at reference laboratories.
Data collected from the medical records included information on demographics such as age, race, gender, and outcome of illness.
This study detected 4,319 episodes of IPD with 20% of cases occurring in children less than 2 years of age.
After the introduction of PCV7, the incidence rates of IPD declined in both blacks and whites and in those less than 2 years of age as wells as those older than 2 years of age—including adults. By 2002, the disparity in IPD incidence rates between white and black children less than 2 years of age had disappeared and was greatly reduced in those over 2 years of age.
There were no changes in the rates of IPD due to non vaccine serotypes in either racial group or in children less than 2 years of age, but—when the data were combined—there was a small increase in non vaccine serotypes in the older group after the introduction of PCV7.
The proportion of antibiotic-nonsusceptible pneumococcal isolates declined among all children less than 2 years of age and among whites older than 2 years of age, eliminating racial differences for antibiotic-nonsusceptibility.
The introduction of PCV7, a vaccine administered exclusively to young children, resulted in a dramatic decline in both invasive and antibiotic-nonsusceptible pneumococcal disease in young children and also in older children and adults. Racial differences in the incidence rates of IPD as well as antibiotic-nonsusceptibility of the S. pneumoniae causing the infection have also been largely eliminated.
This study demonstrated a dramatic impact of infant immunization with PCV7 on the rates of IPD. This effect was across all age and racial groups and was measurable within two years of the introduction of PCV7 despite shortages of vaccine during that period.
In addition, the study reports a reduction of antibiotic-nonsusceptibility among pneumococcal isolates which is also likely attributable to PCV7 immunization of young children.
Other studies have made similar observations as to the effectiveness of this newly introduced vaccine.
In subsequent studies it would be helpful to specifically examine the over 65 year age group—a group with high potential morbidity and mortality—and to look at other populations historically at risk for increased IPD risk, such as Hispanic and native American children.