Rates Of Pneumococcal Disease Research Articles

Validation of a Pediatric Primary Care Network in a US Metropolitan Region as a Community-Based Infectious Disease Surveillance System

This cross-sectional study used Geographic Information System methods to compare sociodemographic and clinical characteristics of children enrolled and not enrolled in a primary care network to determine the suitability of the network to estimate population-based disease rates. We validated the network surveillance system by comparing invasive pneumococcal disease rates between network and nonnetwork children using population-based surveillance data. Among the study population of 130300 children, network children were more likely to be female, Black, non-Hispanic, younger, and receive Medicaid. These differences varied across neighborhoods, however, adjusting for neighborhood characteristics did not significantly change observed differences. Rates of invasive pneumococcal disease were not significantly different between network and non-network children. Significant demographic and clinical differences existed between network and non-network children and varied over small areas. Observed population rates of an infectious disease did not significantly differ suggesting that the network can potentially provide valid disease estimates for the community population.

Infected Acute Subdural Hematoma Associated With Invasive Pneumococcal Disease -Case Report-

A previously healthy 68-year-old woman presented with a rare case of subdural empyema which developed at the site of preceding acute subdural hematoma (SDH). She was first admitted for treatment of an acute SDH after a fall. Since she was neurologically intact and the SDH volume decreased with conservative management, she was discharged 9 days after admission for follow up as an outpatient. Three days after discharge, she unexpectedly returned with worsening headache and altered mental status. Brain computed tomography (CT) showed increased SDH volume. Her condition deteriorated rapidly after presentation, with further increase in SDH volume. Copious pus in addition to the SDH was evacuated by emergency drainage, establishing the diagnosis of subdural empyema. Streptococcus pneumoniae was identified from bacterial cultures. Despite improvement in postoperative CT findings, she fell into septic shock and died 3 days after the drainage. Autopsy revealed meningitis and lobar pneumonia, and the postmortem diagnosis was invasive pneumococcal disease. Infection of acute SDH resulting in subdural empyema by S. pneumoniae is extremely rare. However, invasive pneumococcal disease is not uncommon in the elderly and tends to cause intracranial bleeding. Considering the high mortality rate of invasive pneumococcal disease and the low vaccination rate among the elderly in Japan, neurosurgeons should ask about the pneumococcal vaccination status.

Epidemiology of nasopharyngeal carriage of respiratory bacterial pathogens in children and adults: cross-sectional surveys in a population with high rates of pneumococcal disease

BackgroundTo determine the prevalence of carriage of respiratory bacterial pathogens, and the risk factors for and serotype distribution of pneumococcal carriage in an Australian Aboriginal population.MethodsSurveys of nasopharyngeal carriage of Streptococcus pneumoniae, non-typeable Haemophilus influenzae, and Moraxella catarrhalis were conducted among adults (≥16 years) and children (2 to 15 years) in four rural communities in 2002 and 2004. Infant seven-valent pneumococcal conjugate vaccine (7PCV) with booster 23-valent pneumococcal polysaccharide vaccine was introduced in 2001. Standard microbiological methods were used.ResultsAt the time of the 2002 survey, 94% of eligible children had received catch-up pneumococcal vaccination. 324 adults (538 examinations) and 218 children (350 examinations) were enrolled. Pneumococcal carriage prevalence was 26% (95% CI, 22-30) among adults and 67% (95% CI, 62-72) among children. Carriage of non-typeable H. influenzae among adults and children was 23% (95% CI, 19-27) and 57% (95% CI, 52-63) respectively and for M. catarrhalis, 17% (95% CI, 14-21) and 74% (95% CI, 69-78) respectively. Adult pneumococcal carriage was associated with increasing age (p = 0.0005 test of trend), concurrent carriage of non-typeable H. influenzae (Odds ratio [OR] 6.74; 95% CI, 4.06-11.2) or M. catarrhalis (OR 3.27; 95% CI, 1.97-5.45), male sex (OR 2.21; 95% CI, 1.31-3.73), rhinorrhoea (OR 1.66; 95% CI, 1.05-2.64), and frequent exposure to outside fires (OR 6.89; 95% CI, 1.87-25.4). Among children, pneumococcal carriage was associated with decreasing age (p < 0.0001 test of trend), and carriage of non-typeable H. influenzae (OR 9.34; 95% CI, 4.71-18.5) or M. catarrhalis (OR 2.67; 95% CI, 1.34-5.33). Excluding an outbreak of serotype 1 in children, the percentages of serotypes included in 7, 10, and 13PCV were 23%, 23%, and 29% (adults) and 22%, 24%, and 40% (2-15 years). Dominance of serotype 16F, and persistent 19F and 6B carriage three years after initiation of 7PCV is noteworthy.ConclusionsPopulation-based carriage of S. pneumoniae, non-typeable H. influenzae, and M. catarrhalis was high in this Australian Aboriginal population. Reducing smoke exposure may reduce pneumococcal carriage. The indirect effects of 10 or 13PCV, above those of 7PCV, among adults in this population may be limited.

Sickle cell trait, hemoglobin C trait, and invasive pneumococcal disease.

The cause of historically higher rates of invasive pneumococcal disease among blacks than whites has remained unknown. We tested the hypothesis that sickle cell trait or hemoglobin C trait is an independent risk factor for invasive pneumococcal disease. Eligible children were born in Tennessee (1996-2003), had a newborn screen, enrolled in TennCare aged <1 year, and resided in a Tennessee county with laboratory-confirmed, pneumococcal surveillance. Race/ethnicity was ascertained from birth certificates. Children were followed through 2005 until loss of enrollment, pneumococcal disease episode, fifth birthday, or death. We calculated incidence rates by race/ethnicity and hemoglobin type before and after pneumococcal conjugate vaccine (PCV7) introduction. Poisson regression analyses compared invasive pneumococcal disease rates among blacks with sickle cell trait or hemoglobin C trait with whites and blacks with normal hemoglobin, controlling for age, gender, time (pre-PCV7, transition year, or post-PCV7) and high-risk conditions (eg, heart disease). Over 10 years, 415 invasive pneumococcal disease episodes occurred during 451,594 observed child-years. Before PCV7 introduction, disease rates/100,000 child-years were 2941 for blacks with sickle cell disease, 258 for blacks with sickle cell trait or hemoglobin C trait and 188, 172, and 125 for blacks, whites, and Hispanics with normal hemoglobin. Post-PCV7, rates declined for all groups. Blacks with sickle cell trait or hemoglobin C trait had 77% (95% CI = 22-155) and 42% (95% CI = 1-100) higher rates than whites and blacks with normal hemoglobin. Black children with sickle cell trait or hemoglobin C trait have an increased risk of invasive pneumococcal disease.

Invasive Pneumococcal Disease a Decade after Pneumococcal Conjugate Vaccine Use in an American Indian Population at High Risk for Disease

Before 7-valent pneumococcal conjugate vaccine (PCV7) introduction, invasive pneumococcal disease (IPD) rates among Navajo were several-fold those of the general US population. Only 50% of IPD cases in children involved PCV7 serotypes. We conducted active, population-based surveillance for IPD for the period 1995-2006. We documented case characteristics and serotyped the isolates. Over 12-year period, we identified 1508 IPD cases, 447 of which occurred in children aged <5 years. Rates of IPD due to vaccine serotypes among children aged <1 year, 1 to <2 years, and 2 to <5 years decreased from 210, 263, and 51 cases per 100,000 population, respectively in 1995-1997 to 0 cases in 2004-2006 (P < .001). Among adults aged > or =65 years, rates of IPD due to vaccine serotypes decreased 81% (95% confidence interval, -98% to -9%; P = .02). Rates of nonvaccine serotype IPD were unchanged in all age strata except for persons aged 18 to <40 years, among whom the rate decreased by 35% from 27 to 18 cases per 100,000 population (95% confidence interval, -57% to -1%; P = .03). Vaccine-serotype IPD has virtually been eliminated in the PCV7 era among Navajo of all ages. Overall rates of nonvaccine-serotype IPD have not increased, although increases have occurred for some individual types. Rates of all-serotype IPD among Navajo children remain 3-5-fold greater than in the general US population.

Safety and Immunogenicity of a 13-Valent Pneumococcal Conjugate Vaccine

Invasive pneumococcal disease rates have declined since immunization with 7-valent pneumococcal conjugate vaccine (PCV7) (Prevenar/Prevnar [Wyeth Pharmaceuticals, Philadelphia, PA]) became routine. Certain nonvaccine Streptococcus pneumoniae serotypes (1, 3, 5, 6A, 7F, and 19A) still cause significant morbidity and mortality. The safety and immunogenicity of PCV7 were compared with those of 13-valent PCV (PCV13), which contains saccharides from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F conjugated to CRM(197). Infants were randomly assigned to receive PCV13 or PCV7 at ages 2, 4, and 6 months with other vaccines. Post-third-dose antibodies to each pneumococcal polysaccharide were measured by immunoglobulin G enzyme-linked immunosorbent assay. Antibacterial functional antibodies were measured by opsonophagocytic assay (OPA). Subjects received PCV13 (n = 122) or PCV7 (n = 127). All PCV13 serotypes were immunogenic, with 88% to 98% of infants achieving antibody concentrations of > or =0.35 microg/mL to shared PCV7 serotypes. For the 6 additional serotypes, 97% to 100% of PCV13-vaccinated infants achieved antibody concentrations of > or =0.35 microg/mL. Geometric mean antibody concentration for PCV13 recipients ranged from 1.32 microg/mL (serotype 23F) to 4.26 microg/mL (serotype 14). The ratio of OPA geometric mean titers for the 7 shared serotypes (PCV13:PCV7) ranged from 0.6 to 1.4, suggesting no clinically meaningful differences. For PCV13-only serotypes, OPA geometric mean titers were significantly higher in the PCV13 group than in the PCV7 group. Local reactions and systemic events were similar between groups. PCV13 was well tolerated and immunogenic, with most infants developing antipolysaccharide antibody concentrations of > or =0.35 microg/mL, as well as OPA responses, to each of the 13 serotypes.

Invasive Pneumococcal Disease in Alaskan Children

Alaska Native (AN) children, especially those in the Yukon-Kuskokwim region (YK-AN children), suffer some of the highest rates of invasive pneumococcal disease (IPD) in the world. Rates of IPD declined after statewide introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in 2001, but increased in subsequent years. Population-based laboratory surveillance data (1986-2007) for invasive Streptococcus pneumoniae infection in Alaskan children <5 years old were used to evaluate the association of IPD rates and serotype distribution with immunization, socioeconomic status, and in-home water service. Introduction of PCV7 vaccine resulted in elimination of IPD caused by vaccine serotypes, but was followed by increasing rates of IPD caused by nonvaccine serotypes. Among YK-AN children IPD rates dropped by 60%, but then rose due to non-PCV7 serotypes to levels 5- to 10-fold higher than rates in non-YK-AN children and non-AN children. IPD rates in YK-AN children were twice as high in villages where <10% of houses had in-home piped water compared with villages where more than 80% of houses had in-home piped water (390 cases/100,000 vs. 146 cases/100,000, P = 0.008). High IPD rates in Alaska are associated with lack of in-home piped water (controlling for household crowding and per capita income). The effect of in-home piped water is most likely mediated through reduced water supply leading to limitations on handwashing.

Empyema Hospitalizations Increased in US Children Despite Pneumococcal Conjugate Vaccine

To determine if the incidence of empyema among children in the United States has changed since the introduction of the pneumococcal conjugate vaccine in 2000. We used the nationally representative Kids' Inpatient Database to estimate the annual total number of hospitalizations of children < or = 18 years of age that were associated with empyema in 1997, 2000,2003, and 2006 [corrected]. Using US Census data, estimated counts were converted into annual incidence rates per 100000 children. Incidence rates were compared between 1997 and later years to determine the impact of pneumococcal conjugate vaccine on hospitalization rates. During 2006, an estimated total of 2898 (95% confidence interval [CI]: 2532-3264) hospitalizations of children <or=18 years of age in the United States were associated with empyema. The empyema-associated hospitalization rate was estimated at 3.7 (95% CI: 3.3-4.2) per 100000 children, an increase of almost 70% from the 1997 empyema hospitalization rate of 2.2 (95% CI: 1.9-2.5) per 100000. The rate of complicated pneumonia (empyema, pleural effusion, or bacterial pneumonia requiring a chest tube or decortication) similarly increased 44%, to 5.5 (95% CI: 4.8-6.1) per 100000. The rate of bacterial pneumonia decreased 13%, to 244.3 (95% CI: 231.1-257.5) per 100000. The rate of invasive pneumococcal disease (pneumonia, sepsis, or meningitis caused by Streptococcus pneumoniae) decreased 50%, to 6.3 (95% CI: 5.7-6.9) per 100000. Among children <or=18 years of age, the annual empyema-associated hospitalization rates increased almost 70% between 1997 and 2006, despite decreases in the bacterial pneumonia and invasive pneumococcal disease rates. Pneumococcal conjugate vaccine is not decreasing the incidence of empyema.

Holiday Spikes in Pneumococcal Disease among Older Adults

Rates of invasive pneumococcal disease in the United States increase dramatically during winter holidays. The authors analyzed population-based surveillance data to determine whether spikes may be ...

Epidemiological Evidence for Serotype‐Independent Acquired Immunity to Pneumococcal Carriage

Asymptomatic nasopharyngeal carriage is the main reservoir for transmission of Streptococcus pneumoniae. The rate of both carriage and pneumococcal disease decreases with age. To what extent these changes are the result of developing natural immunity is currently a subject of debate. To study the hypothesis that previous carriage induces serotype-independent protective immunity to new colonization. We compared the rates of pneumococcal acquisition for children with different previous carriage histories. We identified 435 episodes of carriage during the first year of life in follow-up data for 99 Bangladeshi children. Cox regression analysis was adjusted for serotype-specific exposure within the family and other confounding factors. Previous pneumococcal carriage was associated with serotype-independent protection from subsequent acquisition (hazard ratio, 0.60 [95% confidence interval, 0.39-0.90]), whereas recent serotype-specific exposure within the family was associated with an 8-fold increase in the rate of acquisition for that serotype. Our findings are consistent with the hypothesis that serotype-independent protective immunity is stimulated in young children by previous pneumococcal carriage and reduces the rate of new colonization. This immunity has the potential to modulate the development of carriage, irrespective of the colonizing serotype, and to do so starting early in infancy.

Potential Impact of Accelerating the Primary Dose of Pneumococcal Conjugate Vaccine in Infants

To estimate the potential effect of the acceleration of administration of the first dose of pneumococcal conjugate vaccine from 2 months to 6 weeks of age. Prediction model using data from a retrospective cohort study. Published data from 8 states that participated in Active Bacterial Core Surveillance of the Emerging Infections Program Network for pneumococcus before pneumococcal conjugate vaccine introduction (July 1, 1997- June 30, 2000). A total of 759 739 live births under surveillance. Intervention Estimating the potential benefit of administration of the first dose of the pneumococcal conjugate vaccine at 6 weeks of age instead of 2 months of age. Estimation of reduction in the rate of invasive pneumococcal disease in infants 61 to 90 days of age. The estimated direct effect of the acceleration of administration of the first dose of pneumococcal conjugate vaccine from 2 months to 6 weeks of age when this vaccine was first introduced could have reduced the burden of invasive pneumococcal disease in infants 61 to 90 days of age by 39.9%, 56.0%, and 72.1% for respective vaccine efficacies of 50%, 70%, and 90%. This translates into preventing an estimated 73, 103, and 133 cases of invasive pneumococcal disease per year among approximately 4 112 052 live births in the United States. The acceleration of administration of the pneumococcal conjugate vaccine from 2 months to 6 weeks of age could reduce the burden of invasive pneumococcal disease among infants. This observation may be important when a new conjugate vaccine becomes available, particularly among populations with prevalent invasive pneumococcal disease from a serotype included in the new vaccine.

Serotypes and antimicrobial susceptibilities of invasive Streptococcus pneumoniae pre- and post-seven valent pneumococcal conjugate vaccine introduction in Alberta, Canada, 2000–2006

Alberta, Canada introduced the Streptococcus pneumoniae seven valent conjugate vaccine (PCV7) program for children less than 2 years of age in September 2002. We determined the rates of invasive pneumococcal disease in Alberta, Canada 2 years pre- and 4 years post-PCV7 introduction (2000–2006) as well as the rates of antibiotic resistance and serotype distribution in this same time period. Overall, PCV7 serotypes decreased 61% from 2000 to 2006. The greatest decrease in incidence of invasive pneumococcal disease occurred in children less than 2 years of age declining from a high of 96.7/100,000 (2000) to 25.8/100,000 (2006) ( P < 0.0001). Non-susceptibility of S. pneumoniae isolates to penicillin dropped significantly from 14% in 2000 to 4.6% in 2006 ( P < 0.0001). Non-susceptible erythromycin isolates also decreased from 8.8% (2000) to 5.8% (2006) ( P = 0.13). The introduction of PCV7 in Alberta, Canada has decreased the incidence of invasive pneumococcal disease in Alberta as well as resulting in a decrease in antibiotic resistance over this same time frame, principally for penicillin resistance.

Standardizing Surveillance of Pneumococcal Disease

Surveillance for invasive pneumococcal disease has been conducted using a variety of case ascertainment methods and diagnostic tools. Interstudy differences in observed rates of invasive pneumococcal disease could reflect variations in surveillance methods or true epidemiological differences in disease incidence. To facilitate comparisons of surveillance data among countries, investigators of Pneumococcal Vaccines Accelerated Development and Introduction Plan-sponsored projects have developed standard case definitions and data reporting methods. Investigators developed case definitions for meningitis, pneumonia, and very severe disease using existing World Health Organization guidelines and clinical definitions from Africa and Asia. Standardized case definitions were used to standardize reporting of aggregated results. Univariate analyses were conducted to compare results among countries and to identify factors contributing to detection of Streptococcus pneumoniae. Surveillance sites varied with regard to the age groups targeted, disease syndromes monitored, specimens collected, and laboratory methods employed. The proportion of specimens positive for pneumococcus was greater for cerebrospinal fluid specimens (1.2%-19.4%) than for blood specimens (0.1%-1.4%) in all countries (range, 1.3-38-fold greater). The distribution of disease syndromes and pneumonia severity captured by surveillance differed among countries. The proportion of disease cases with pneumococcus detected varied by syndrome (meningitis, 1.4%-10.8%; pneumonia, 0.2%-1.3%; other, 0.2%-1.2%) and illness severity (nonsevere pneumonia, 0%-2.7%; severe pneumonia, 0.2%-1.2%), although these variations were not consistent for all sites. Antigen testing and polymerase chain reaction increased the proportion of cerebrospinal fluid specimens with pneumococcus identified by 1.3-5.5-fold, compared with culture alone. Standardized case definitions and data reporting enhanced our understanding of pneumococcal epidemiology and enabled us to assess the contributions of specimen type, disease syndrome, pneumonia severity, and diagnostic tools to rate of pneumococcal detection. Broader standardization and more-detailed data reporting would further improve interpretation of surveillance results.

Surveillance of Pneumococcal‐Associated Disease among Hospitalized Children in Khanh Hoa Province, Vietnam

To understand the epidemiology of childhood bacterial diseases, including invasive pneumococcal disease, prospective surveillance was conducted among hospitalized children in Nha Trang, Vietnam. From April 2005 through August 2006, pediatricians at the Khanh Hoa General Hospital used standardized screening criteria to identify children aged <5 years who had signs and symptoms of invasive bacterial disease. All cerebrospinal fluid (CSF) and blood specimens collected were tested by bacterial culture. Selected culture-negative specimens were tested for Streptococcus pneumoniae by antigen detection or for Haemophilus influenzae, Moraxella catarrhalis, Neisseria meningitidis, and S. pneumoniae by polymerase chain reaction (PCR). A total of 987 children were enrolled (794 with pneumonia, 76 with meningitis, and 117 with other syndromes consistent with invasive bacterial disease); 84% of children were aged 0-23 months, and 57% were male. Seven (0.71%) of 987 blood cultures and 4 (15%) of 26 CSF cultures were positive for any bacterial pathogen (including 6 for H. influenzae type b and 1 for S. pneumoniae). Pneumococcal antigen testing and PCR identified an additional 16 children with invasive pneumococcal disease (12 by antigen testing and 4 by PCR). Among children aged <5 years who lived in Nha Trang, the incidence rate of invasive pneumococcal disease was at least 48.7 cases per 100,000 children (95% confidence interval, 27.9-85.1 cases per 100,000 children). S. pneumoniae and H. influenzae type b were the most common causes of laboratory-confirmed invasive bacterial disease in children. PCR and antigen testing increased the sensitivity of detection and provided a more accurate estimate of the burden of invasive bacterial disease in Vietnam.

Experience with pneumococcal conjugate vaccine in Norway

Seven-valent pneumococcal conjugate vaccine (PCV7) was introduced into the Norwegian childhood vaccination program in July 2006 in a 2+1 dose (three-dose) schedule. Vaccine coverage quickly reached high levels and the incidence rate of invasive pneumococcal disease in children under 2 years of age declined rapidly. The vaccine program’s effectiveness was estimated to be 74%.

PCR-Based Quantitation and Clonal Diversity of the Current Prevalent Invasive Serogroup 6 Pneumococcal Serotype, 6C, in the United States in 1999 and 2006 to 2007

Following introduction of the 7-valent pneumococcal conjugate vaccine to the United States, rates of invasive pneumococcal disease (IPD) caused by serotype 6A declined among all age groups, while rates of IPD caused by newly identified serotype 6C increased slightly among persons 5 years of age and older. Conventionally serotyped 6A isolates (CS6As) from active population-based surveillance during 1999 and 2006 to 2007 were classified as serotypes 6A and 6C by an expedient and highly accurate serotype 6C-specific PCR assay developed during this study. PCR testing of 636 year 1999, 2006, and 2007 CS6As revealed 6C proportions of 35/214 (16.4%), 141/218 (64.7%), and 141/204 (69.1%), respectively. These results agreed with those from a previously devised monoclonal antibody-based serotyping system (346 CS6As compared). Type 6C IPD incidence significantly increased during 2006 and 2007 compared to during 1999 (0.57 to 0.58 cases per 100,000 and 0.22 cases per 100,000, respectively; 164% increase from 1999 to 2007 [95% confidence interval, 87 to 270%]), while rates of IPD due to types 6A and 6B markedly decreased. In 2007, 31.2% of 6C isolates were not susceptible to penicillin. Serotype 6C is now the predominant serotype associated with serogroup 6 IPD in the United States and is often penicillin nonsusceptible. We performed multilocus sequence typing (MLST) on a limited sampling of 6C isolates with different antimicrobial susceptibility profiles. MLST of 42 6C isolates revealed 12 genotypes distributed among six distinct genetic groups. Fifteen 6C isolates shared one of four different MLST types with 6C-negative CS6As. MLST results suggest 6C strains arose from independent recombination events involving only serotype 6A and 6C parental strains.

Association of respiratory virus activity and environmental factors with the incidence of invasive pneumococcal disease

To correlate the incidence rate of invasive pneumococcal disease (IPD) with fluctuations in respiratory virus activity and environmental factors in Christchurch, New Zealand. Ecological study comparing incidence rates of IPD with incidence rates of respiratory virus detection, meteorologic and air pollution data during 1995-2006. The relationship between annualized monthly rates of IPD and annualized monthly rates of respiratory virus detection and monthly meteorologic recordings and air pollution data was assessed using Spearman's rank correlation coefficient and negative binomial regression analysis. Incidence rates of IPD were statistically significantly correlated with increasing detection rates of influenza viruses, respiratory syncytial virus (RSV), adenovirus and parainfluenza virus 3. Furthermore, rates of IPD were statistically significantly correlated with decreasing daily temperature, sunshine hours and wind speed, and with increasing air pollution levels and humidity. After regression analysis, the only statistically significant associations in the total population were between influenza virus activity, parainfluenza virus 3 activity and air pollution levels and increased rates of IPD, although RSV activity was associated with increased rates of IPD in children <5 years old. Incidence rates of IPD are associated with the increased activity of some respiratory viruses and with air pollution in Christchurch.

Vaccines: Pneumococcal Vaccination of Elderly Adults: New Paradigms for Protection

Pneumococcal polysaccharide vaccine has been licensed for use in the United States for >30 years, and two-thirds of the elderly population in the United States have received this vaccine. Observational studies have demonstrated that pneumococcal polysaccharide vaccine reduces the risk of invasive pneumococcal disease in immunocompetent elderly individuals, but neither observational studies nor clinical trials have demonstrated consistent evidence for a reduction in the incidence of pneumonia in vaccinated older adults. The introduction of pneumococcal protein conjugate vaccine among children has led to a herd immunity effect that has resulted in a 38% decrease in the rate of invasive pneumococcal disease among elderly adults. The high efficacy of pneumococcal protein conjugate vaccine in children has renewed interest in evaluating pneumococcal protein conjugate vaccines in adults for prevention of invasive pneumococcal disease and pneumonia. Moreover, the recognition of the presence and function of noncapsular pneumococcal protein antigens and the increasing availability of adjuvants highlight the promise of new vaccination strategies to decrease the burden of pneumococcal infection in this high-risk population.

Indirect Effect of 7‐Valent Pneumococcal Conjugate Vaccine on Pneumococcal Colonization among Unvaccinated Household Members

Since the introduction of 7-valent pneumococcal conjugate vaccine (PCV7) in the United States, rates of invasive pneumococcal disease have decreased in both vaccinated and unvaccinated age groups. Reduction of invasive pneumococcal disease in unvaccinated groups has been attributed to reduced transmission of vaccine-type pneumococci in the community. Understanding the impact of PCV7 on carriage among vaccinated and unvaccinated community members is critical to interpreting, predicting, and understanding the impact of PCV7 on disease. A group-randomized, phase III efficacy trial of PCV7 was conducted among southwestern American Indian communities. Meningococcal conjugate vaccine against serogroup C was used as the control. After the trial was unblinded, we conducted a carriage study of participating communities to evaluate the impact of PCV7 on colonization among trial participants and their unvaccinated household members. Adults and unvaccinated children aged <5 years living in households with a PCV7 vaccinee were less likely to be colonized with vaccine-type pneumococci (odds ratio [OR] for adults, 0.57; 95% confidence interval [CI], 0.33-0.99; OR for children, 0.57; 95% CI, 0.26-0.98) than were those living in a household with a control vaccinee. There was no difference for children aged 5-17 years. Decreases in vaccine-type carriage were offset by increases in carriage of nonvaccine types. Among adults living with a trial participant colonized with vaccine-type pneumococcus, those in the households randomized to receive PCV7 were less likely to be colonized with the same serotype than were those in the households randomized to receive the control vaccine (OR, 0.34; 95% CI, 0.11-0.99). Vaccine-type pneumococcal carriage was lower among adults and unvaccinated children living with a PCV7 vaccinee. This is attributable to reduced exposure and reduced transmission when exposure occurs.

Editorial Commentary:Changing Epidemiology of Invasive Pneumococcal Disease: A Complicated Story

jugate vaccine into the WMA population in Arizona. This study is very beneficial to our understanding of the dynamics of pneumococcal epidemiology in general and of the impact, both positive and negative, that vaccine introduction may have in a population. The study performed by Lacapa et al. [2] was an observational study and compared rates of disease in the time period before vaccine introduction with rates in the time period after vaccine introduction. One of the key observations of the study was that the incidence of invasive disease due to the 7 serotypes covered in the vaccine was reduced substantially in this highrisk population. The observed 92% reduction in the rate of infectious pneumococcal disease among high-risk children aged !5 years is consistent with the reductions observed in other studies. However, the rate of disease among vaccinated WMA children still remains higher than that among the general population. There are 2 reasons for this. First, given the higher initial rate of disease, a 92% reduction in the rate of disease still leaves a substantial disease burden in the population. Second, prior to vaccine introduction, the proportion of overall invasive disease due to the 7 serotypes covered in the vaccine was only 56.2% among WMA children, compared with ∼90% in the general population. The reasons for this difference are not known, but the difference is consistent with both the variability of coverage of the 7-valent conjugate vaccine globally and with changes in serotype distribution observed over time in the Native American population and other populations globally. Although other vaccines that contain 10 and 13 pneumococcal serotypes are in development and would provide broader coverage, until we better understand the reasons that serotype distributions vary geographically and over time, strategic vaccine design will be hampered.