Aaron M. Wendelboe

Duration of immunity against pertussis after natural infection or vaccination.

Despite decades of high vaccination coverage, pertussis has remained endemic and reemerged as a public health problem in many countries in the past 2 decades. Waning of vaccine-induced immunity has been cited as one of the reasons for the observed epidemiologic trend. A review of the published data on duration of immunity reveals estimates that infection-acquired immunity against pertussis disease wanes after 4–20 years and protective immunity after vaccination wanes after 4–12 years. Further research into the rate of waning of vaccine-acquired immunity will help determine the optimal timing and frequency of booster immunizations and their role in pertussis control.

Transmission of bordetella pertussis to Young Infants

Background: Pertussis vaccination has reduced the number of notified cases in industrialized countries from peak years by more than 95%. The effect of recently recommended adult and adolescent vaccination strategies on infant pertussis depends, in part, on the proportion of infants infected by adults and adolescents. This proportion, however, remains unclear, because studies have not been able to determine the source case for 47%–60% of infant cases. Methods: A prospective international multicenter study was conducted of laboratory confirmed infant pertussis cases (aged ≤6 months) and their household and nonhousehold contacts. Comprehensive diagnostic evaluation (including PCR and serology) was performed on all participants independent of symptoms. Source cases were identified and described by relationship to the infant, age and household status. Results: The study population comprised 95 index cases and 404 contacts. The source of pertussis was identified for 48% of infants in the primary analysis and up to 78% in sensitivity analyses. In the primary analysis, parents accounted for 55% of source cases, followed by siblings (16%), aunts/uncles (10%), friends/cousins (10%), grandparents (6%) and part-time caretakers (2%). The distribution of source cases was robust to sensitivity analyses. Conclusions: This study provides solid evidence that among infants for whom a source case was identified, household members were responsible for 76%–83% of transmission of Bordetella pertussis to this high-risk group. Vaccination of adolescents and adults in close contact with young infants may thus eliminate a substantial proportion of infant pertussis if high coverage rates can be achieved.

Relationships between body mass indices and surgical replacements of knee and hip joints

BACKGROUND Osteoarthritis is both the most common form of arthritis and the most common reason for joint replacement surgery. Obese persons are believed to be more likely to develop generalized osteoarthritis that leads not only to knee but also to hip joint replacement surgeries. We hypothesized that obesity is also a risk for partial joint replacements and surgical revisions. METHODS A frequency-matched case-control study was conducted in Utah. Between 1992 and 2000, 840 hip and 911 knee joint replacement surgery patients, aged 55 to 74 years, were included in this study. Cases were randomly matched to 5578 controls, defined as Utah residents enrolled in a cancer screening trial. Odds ratios (ORs) were calculated using ICD-9 (International Classification of Diseases, 9th revision) procedural codes and body mass index (BMI) groups. RESULTS There was a strong association between increasing BMI and both total hip and knee replacement procedures. In males, the highest OR was for those weighing 37.50 to 39.99 kg/m(2) (total hip: OR=9.37, 95% confidence interval [CI] 2.64-33.31; total knee: OR=16.40; 95% CI 5, 19-51.86). In females, the highest OR was for those weighing > or =40 kg/m(2) (total hip: OR=4.47; 95% CI, 2.13-9.37; total knee: OR=19.05; 95% CI, 9.79-37.08). There were slight gender-specific differences in risk found for partial hip replacement procedures. Unexpectedly, no statistically significant association was found between obesity and the risk for hip or knee revision procedures. CONCLUSIONS While there is an association between obesity and hip and knee joint replacement surgeries, obesity does not appear to confer an independent risk for hip or knee revision procedures.

Spinach-associated Escherichia coli O157:H7 Outbreak, Utah and New Mexico, 2006

In 2006, Utah and New Mexico health departments investigated a multistate cluster of Escherichia coli O157:H7. A case–control study of 22 case-patients found that consuming bagged spinach was significantly associated with illness (p<0.01). The outbreak strain was isolated from 3 bags of 1 brand of spinach. Nationally, 205 persons were ill with the outbreak strain.

Role of maternal pertussis antibodies in infants

Pertussis remains a serious infection in young infants. Most deaths occur in the first 3 months of life, before administration of the first dose of pertussis vaccine. Pertussis antibodies are transferred from mother to infant; but because of the lack of serologic correlates of protection, it is difficult to determine the proportion of infants born with a protective concentration of maternal antibodies. Indirect evidence suggests that maternal antibodies provide short lived protection against fatal pertussis. It is hoped that the protection of young infants could be enhanced by maternal or neonatal vaccination. The possibility of protecting young infants against pertussis by immunizing their mothers during pregnancy was investigated in the 1930s and 1940s; no further studies have been published since. Recent animal and human studies have provided evidence that neonatal immunization with acellular pertussis vaccine can efficiently prime T and B cells and act as a basis for future immune response. The limited data on neonatal and maternal pertussis immunization are promising and call for further research to reduce the vulnerability of young infants to pertussis disease.

Associations between body-mass index and surgery for rotator cuff tendinitis.

BACKGROUND Rotator cuff tendinopathy is a common entity. We hypothesized that obesity, because of biomechanical and systemic risk factors, increases the risks of rotator cuff tendinitis, tears, and related surgical procedures. METHODS A frequency-matched case-control study was conducted. Three hundred and eleven patients who were fifty-three to seventy-seven years old and who underwent rotator cuff repair, arthroscopy, and/or other repair of the shoulder in a large hospital from 1992 to 2000 were included in the study. These surgical procedures were used as proxies for the risk of rotator cuff tendinitis. These patients were age and frequency-matched to 933 controls, who were randomly drawn from a pool of 10,943 potential controls consisting of Utah state residents who were enrolled in a large cancer-screening trial. Age-adjusted odds ratios were calculated with use of the International Classification of Diseases, Ninth Revision procedural codes and body-mass-index groups. The data were stratified according to gender and age. Multiple linear regression analyses also were performed. RESULTS There was an association between increasing body-mass index and shoulder repair surgery. The highest odds ratios for both men (odds ratio = 3.13; 95% confidence interval = 1.29 to 7.61) and women (odds ratio = 3.51; 95% confidence interval = 1.80 to 6.85) were for individuals with a body-mass index of > or =35.0 kg/m(2). Tests for trend also were highly significant for both men (p = 0.002) and women (p < or = 0.001). Multiple linear regression analysis also indicated a significant association between increasing body-mass index and shoulder surgery (beta = 1.57; 95% confidence interval = 0.97 to 2.17; p < or = 0.001). CONCLUSIONS There is an association between obesity and shoulder repair surgery in men and women who are fifty-three to seventy-seven years of age. The results of the present study suggest that increasing body-mass index is a risk factor for rotator cuff tendinitis and related conditions.

Comparison of Serological and Real-Time PCR Assays To Diagnose Bordetella pertussis Infection in 2007

ABSTRACT Bacterial culture for diagnosing pertussis infection has high specificity but poor sensitivity and is slow. Highly sensitive real-time PCR assays and single-serum pertussis serology have been developed to overcome these limitations, but there are few data available on the relative sensitivities and specificities of such assays for pertussis diagnosis. Using data on 195 participants (≥7 years old) from an epidemiological study, we assessed the sensitivity, specificity, and performance (Youden index) for pertussis diagnosis of the pertussis toxin enzyme-linked immunosorbent assay (using single and paired serology) and of real-time PCR assays (using the IS481 and ptxA-Pr targets). All available diagnostic information (clinical and laboratory) was pooled to serve as the gold standard. Single serology was the most efficient diagnostic test (Youden index, 0.57 to 0.58), with relatively high sensitivity (>64%) and high specificity (>90%), independent of the cutoff level. IS481 PCR performance was superior to that of ptxA-Pr PCR, and it was the second-most-efficient tool (Youden index, 0.30). Performing both ptxA-Pr and IS481 PCRs did not improve diagnostic performance. The greatest test efficiency (Youden index, 0.69 to 0.74) was achieved when single-serum serology was used in combination with IS481 or ptxA-Pr PCR or paired serology. Combining single serology with one PCR or paired serology increased the sensitivity with an associated limited decrease in specificity. The most specific tests for diagnosis of pertussis were single serology and ptxA-Pr PCR, and the most sensitive diagnostic tool was the combination of IS481 PCR with single serology.

Estimating the role of casual contact from the community in transmission of Bordetella pertussis to young infants

The proportion of infant pertussis cases due to transmission from casual contact in the community has not been estimated since before the introduction of pertussis vaccines in the 1950s. This study aimed to estimate the proportion of pertussis transmission due to casual contact using demographic and clinical data from a study of 95 infant pertussis cases and their close contacts enrolled at 14 hospitals in France, Germany, Canada, and the U.S. between February 2003 and September 2004. A complete case analysis was conducted as well as multiple imputation (MI) to account for missing data for participants and close contacts who did not participate. By considering all possible close contacts, the MI analysis estimated 66% of source cases were close contacts, implying the minimum attributable proportion of infant cases due to transmission from casual contact with community members was 34% (95% CI = 24%, 44%). Estimates from the complete case analysis were comparable but less precise. Results were sensitive to changes in the operational definition of a source case, which broadened the range of MI point estimates of transmission from casual community contact to 20%–47%. We conclude that casual contact appears to be responsible for a substantial proportion of pertussis transmission to young infants.Medical subject headings (MeSH): multiple imputation, pertussis, transmission, casual contact, sensitivity analysis, missing data, community.

Diagnosis of pertussis: a historical review and recent developments

The accurate and timely diagnosis of pertussis continues to be challenging. The widespread use of pertussis vaccines has dramatically altered the epidemiology and clinical presentation of pertussis disease, such that many cases do not present with the hallmark symptoms, such as inspiratory whoop, post-tussive vomiting and paroxysmal cough. A variety of laboratory tools are available to aid in the diagnosis of pertussis, including culture, direct fluorescent antibody testing, PCR, and paired and single serology techniques. This article reviews the strengths and limitations, including the sensitivity and specificity, of each of these diagnostic tools.

Thrombosis: A major contributor to global disease burden

Thrombosis is a common pathology underlying ischemic heart disease, ischemic stroke, and venous thromboembolism (VTE). The Global Burden of Disease Study 2010 (GBD 2010) documented that ischemic heart disease and stroke collectively caused one in four deaths worldwide. GBD 2010 did not report data for VTE as a cause of death and disability. We performed a systematic review of the literature on the global disease burden due to VTE in low, middle and high income countries. Studies from Western Europe, North America, Australia, and Southern Latin America (Argentina) yielded consistent results with annual incidences ranging from 0.75 to 2.69 per 1,000 individuals in the population. The incidence increased to between 2 and 7 per 1,000 among those 70 years of age or more. Although the incidence is lower in individuals of Chinese and Korean ethnicity, their disease burden is not low because of population aging. VTE associated with hospitalization was the leading cause of disability-adjusted-life-years (DALYs) lost in low and middle income countries, and second in high income countries, responsible for more DALYs lost than nosocomial pneumonia, catheter-related blood stream infections, and adverse drug events. VTE causes a major burden of disease across low, middle, and high income countries. More detailed data on the global burden of VTE should be obtained to inform policy and resource allocation in health systems, and to evaluate if improved utilization of preventive measures will reduce the burden.