Biomedical subjects
M Wharton
Publications and source records attributed to M Wharton.
Tetanus surveillance--United States, 1991-1994.
PROBLEM/CONDITION: Despite the widespread availability of a safe and effective vaccine against tetanus, 201 cases of the disease were reported during 1991-1994. Of patients with known illness outcome, the case-fatality rate was 25%. REPORTING PERIOD COVERED: 1991-1994. DESCRIPTION OF SYSTEM: Physician-diagnosed cases of tetanus are reported to local and state health departments, the latter of which reports these cases on a weekly basis to CDC's National Notifiable Disease Surveillance System. Since 1965, state health departments also have submitted supplemental clinical and epidemiologic information to CDC's National Immunization Program. RESULTS: During 1991-1994, 201 cases of tetanus were reported from 40 states, for an average annual incidence of 0.02 cases per 100,000 population. Of the 188 patients for whom age was known, 101 (54%) were aged > or = 60 years and 10 (5%) were aged < 20 years. No cases of neonatal tetanus were reported. Among adults, the risk for tetanus increased with age; the risk for persons aged > or = 80 years was more than 10 times greater than the risk for persons aged 20-29 years. All deaths occurred among persons aged > or = 30 years. The case-fatality rate (overall: 25%) increased with age, from 11% in persons aged 30-49 years to 54% in persons aged > or = 80 years. Only 12% of all patients were reported to have received a primary series of tetanus toxoid before onset of illness. For 77% of patients, tetanus occurred after an acute injury was sustained. Of patients who obtained medical care for their injury, only 43% received tetanus toxoid as part of wound prophylaxis. INTERPRETATION: The epidemiology of reported tetanus in the United States during 1991-1994 was similar to that during the 1980s. Tetanus continued to be a severe disease primarily of older adults who were unvaccinated or inadequately vaccinated. Most tetanus cases occurred after an acute injury was sustained, emphasizing the need for appropriate wound management. ACTIONS TAKEN: In addition to decennial booster doses of tetanus-diphtheria toxoid during adult life, the Advisory Committee on Immunization Practices (ACIP) recommends vaccination visits for adolescents at age 11-12 years and for adults at age 50 years to enable health-care providers to review vaccination histories and administer any needed vaccine. Full implementation of the ACIP recommendations should virtually eliminate the remaining tetanus burden in the United States.
Effectiveness of the pertussis vaccination program as determined by use of the screening method: United States, 1992-1994.
The screening method was used to evaluate the effectiveness of the pertussis vaccination program in the United States during 1992-1994. The formula VE = 1 - [PCV/(1 - PCV)][(1 - PPV)/PPV] was used (VE = vaccine effectiveness; PCV = proportion of cases vaccinated; PPV = proportion of population vaccinated). Data from the national Supplementary Pertussis Surveillance System and the National Health Interview Survey were used to determine PCV and PPV, respectively. Among children aged 7-18 months, VE for 3 doses of pertussis vaccine was 79% (95% confidence interval, 74%-83%) for preventing culture-confirmed pertussis. Between the ages of 19 and 47 months, VE for > or = 4 doses was 90% (95% confidence interval, 88%-92%). VE estimates appeared lower in epidemic (1993) than non-epidemic years (1992, 1994). VE estimates determined using the screening method were consistent with the previous estimates from the United States. This method will continue to be useful for assessing the effectiveness of the pertussis vaccination program in the United States, where acellular pertussis vaccines are recommended for infants.
The epidemiology of varicella-zoster virus infections.
Historically, varicella has been a disease predominantly affecting preschool and school-aged children in the United States. The live attenuated varicella vaccine was licensed in this country in 1995 and has been recommended for routine use in immunization of children 12 to 18 months of age. As an increasing proportion of the children in the United States are protected from varicella by vaccination, changes in the current epidemiology of the disease are anticipated. This article reviews the current epidemiology of VZV infection and outlines issues related to possible changes in varicella epidemiology that may follow widespread use of the live varicella (Oka) vaccine.
Risk factors for pertussis in young infants during an outbreak in Chicago in 1993.
Because young infants are at highest risk for severe pertussis and death and are also too young to have received the minimal protective series of three doses of diphtheria-tetanus-pertussis (DTP) vaccine, we conducted a matched case-control study to assess risk factors for pertussis among young infants during a pertussis outbreak in Chicago in 1993. We enrolled 39 cases < 7 months of age from a single teaching hospital and 96 controls, individually matched for age, from the well-child clinic at the same hospital. Demographic characteristics, immunization status, and opportunities for disease exposure were analyzed by means of conditional logistic regression. Cases and controls were similarly up to date with their DTP vaccinations (87% and 89%, respectively). Infants of adolescent mothers (matched odds ratio [OR], 6.4; 95% confidence interval [CI], 1.3-41.4) and infants of mothers who suffered > or = 7 days of cough during the child's incubation period (matched OR, 12.0; 95% CI, 1.4 to infinity) were significantly more likely to have pertussis. Young mothers and mothers with a cough lasting > or = 7 days may be an important source of pertussis infection for their young infants.
Molecular epidemiology of diphtheria in Russia, 1985-1994.
The largest diphtheria outbreak in the developed world since the 1960s began in the Russian federation in 1990. One hundred fifty-six Corynebacterium diphtheriae strains from throughout Russia, selected for temporal and geographic diversity, were assayed by ribotyping and multilocus enzyme electrophoresis (MEE). These tests showed significant genetic diversity within the C. diphtheriae species, and ribotyping and MEE data generally correlated well with epidemiologic data. A distinct clonal group of C. diphtheriae isolates (ET 8 complex) emerged in Russia in 1990 as the current outbreak began, and as the outbreak has progressed, these organisms have made up increasingly larger proportions of the strains that are isolated. Furthermore, the main characteristic of the epidemic strains is a specific combination of ET 8 and ribotypes G1 and G4. This study confirms the epidemiologic utility of the molecular subtyping methods that detected the epidemic clone and addresses the clone's origin and relation to C. diphtheriae from throughout Russia.
Pertussis deaths: report of 23 cases in the United States, 1992 and 1993.
OBJECTIVE: To characterize pertussis deaths and to identify possible risk factors and prevention strategies. METHODS: A retrospective review of all deaths attributed to pertussis with disease onset during 1992 and 1993 reported to the Centers for Disease Control and Prevention. Hospital discharge summaries and autopsy reports were reviewed, and additional clinical information was provided by physicians involved in the care of the children. RESULTS: During 1992 and 1993, 23 deaths attributed to pertussis were reported to the Centers for Disease Control and Prevention. Cultures for Bordetella pertussis were positive in 18 (90%) of the 20 cases in which it was performed. Twenty (87%) of the 23 children who died were young than 1 year of age, and 18 (78%) of the children had received no doses orf pertussis vaccine. Among 20 children for whom gestational ages were known, 12 (60%) were born at36 weeks' gestation or earlier; in contrast, 10.7% of live births in the United States in 1992 were at 36 weeks' gestation or earlier. The median age of mothers whose children had fatal pertussis was 20 (range, 14 to 37) years in the 15 cases in which ages were known, compared with the national median age of 26.3 years in 1992. Pneumonia was a complication in all but 1 (96%) of the cases. Seizures occurred in 4 cases (17%), and acute encephalopathy occurred in 3 cases (13%). CONCLUSIONS: Pertussis continues to cause serious illness and death in the United States, particularly among infants who are not vaccinated. Preterm delivery and young maternal age may place infants at increased risk of death because of pertussis. Under the current pertussis vaccination schedule, three fourths of the infants who died were too young to have received three doses of pertussis vaccine, the minimum number of doses considered necessary for adequate protection against clinical pertussis. Additional strategies, to prevent deaths caused by pertussis in young infants, such as starting infant vaccination at an earlier age and booster doses to adolescents and adults, need to be evaluated.
The measles-mumps-rubella vaccination program in Finland.
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Are we ready for diphtheria? A report from the Diphtheria Diagnostic Workshop, Atlanta, 11 and 12 July 1994.
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Pertussis infection among adults during the 1993 outbreak in Chicago.
To evaluate the role of adults in the transmission of pertussis during an epidemic, persons presenting with unexplained cough to ambulatory care clinics were evaluated for evidence of pertussis infection. Nasopharyngeal specimens for culture and serum samples for IgG and IgA antibodies to filamentous hemagglutinin and pertussis toxin antigens of Bordetella pertussis were obtained. Thirty-eight adults were enrolled in the study; 10 (26%) had serologic evidence of B. pertussis infection. Clinical findings were not significantly different among persons with and without evidence of pertussis infection. Pertussis should be considered in the differential diagnosis of persistent cough in all age groups. Future use of new acellular pertussis vaccines in adults may substantially impact the control of the infection.
Vaccine-associated paralytic poliomyelitis in the United States: no evidence of elevated risk after simultaneous intramuscular injections of vaccine.
During the past 30 years, Romania reported rates of vaccine-associated paralytic poliomyelitis (VAPP) approximately 10-fold higher than in the United States. The elevated VAPP risk was largely caused by multiple intramuscular (im) injections with antibiotics given within 30 days of onset of paralysis. Because it is not known whether im injections contribute to the VAPP risk in the United States, we examined VAPP cases reported since 1980. We reviewed injection histories of VAPP cases reported to the Centers for Disease Control and Prevention from 1980 to 1993: with vaccines for 1980 to 1987; and for all substances for 1988 to 1993. Rates of VAPP by number of im injections with vaccines were calculated from 1988 to 1993 with estimated vaccine coverage data from the National Health Interview Survey. From 1980 to 1993 a total of 119 cases of poliomyelitis were reported to the Centers for Disease Control and Prevention. Of these, 87 (73%) were vaccine-associated and immunologically normal: 41 were oral polio vaccine (OPV) recipient cases; 40 were OPV contact cases; and 6 were community-acquired cases. A history of im injections in the 45 days before onset of paralysis was obtained from 28 (72%) of 39 recipient cases reported from 1980 to 1993 for which dates of paralysis onset could be determined and from 1 (8%) of 13 contact cases reported from 1988 to 1993. With one exception all substances administered intramuscularly were routine childhood vaccines. No clustering of im injections in the "high risk" windows, 0 to 3 and 8 to 21 days before onset of paralysis, was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Application of PCR for detection of toxigenic Corynebacterium diphtheriae strains isolated during the Russian diphtheria epidemic, 1990 through 1994.
A total of 250 Corynebacterium diphtheriae isolates from clinical cases and carriers in Russia were assayed by PCR directed at the A subunit of the diphtheria toxin gene to distinguish toxigenic from nontoxigenic strains; 170 strains were positive as indicated by the presence of the 248-bp amplicon. The results of this PCR assay were in complete concordance with those of the standard immunoprecipitation assay (Elek), and the PCR assay is a useful tool for rapid identification in clinical laboratories.
The 1993 pertussis epidemic in Cincinnati.
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Theoretical epidemiologic and morbidity effects of routine varicella immunization of preschool children in the United States.
The authors studied the effects of routine varicella immunization of US preschool children and of implementation of a catch-up program in older children on the age distribution of cases and on overall morbidity, with emphasis on the sensitivity of the results to level of vaccine coverage, duration of protection, responsiveness to boosting, relative residual susceptibility and infectiousness, and degree of morbidity among vaccine breakthrough cases. An age-structured theoretical transmission model was used, with values for vaccine efficacy based on a review of the literature by an expert panel. Although implementation of a vaccination program resulted in a shift in the age distribution of remaining varicella cases toward older ages with higher complication rates, the overall reduction in cases resulted in decreased morbidity as measured by overall number of hospitalizations and number of primary cases. Routine immunization with live-virus varicella vaccine would probably result in a substantial reduction in the number of uncomplicated primary cases of chickenpox, as well as a decreased number of complicated cases requiring hospitalization. The number and age distribution of vaccinated cases would depend strongly on the characteristics of the vaccine. Vaccine efficacy studies in the field should be designed to obtain better estimates of residual susceptibility, residual infectiousness, duration of protection, and effects of boosting by wild-type reinfection.
Cost-effectiveness of a routine varicella vaccination program for US children.
OBJECTIVE: To evaluate the economic consequences of a routine varicella vaccination program that targets healthy children. METHODS: Decision analysis was used to compare the costs, outcomes, and cost-effectiveness of a routine vaccination program with no intervention. Clinical outcomes were based on a mathematical model of vaccine efficacy that relied on published and unpublished data and on expert opinion. Medical utilization rates and costs were collected from multiple sources, including the Kaiser Permanente Medical Care Program and the California Hospital Discharge Database. RESULTS: A routine varicella vaccination program for healthy children would prevent 94% of all potential cases of chickenpox, provided the vaccination coverage rate is 97% at school entry. It would cost approximately $162 million annually if one dose of vaccine per child were recommended at a cost of $35 per dose. From the societal perspective, which includes work-loss costs as well as medical costs, the program would save more than $5 for every dollar invested in vaccination. However, from the health care payer's perspective (medical costs only), the program would cost approximately $2 per chickenpox case prevented, or $2500 per life-year saved. The medical cost of disease prevention was sensitive to the vaccination coverage rate and vaccine price but was relatively insensitive to assumptions about vaccine efficacy within plausible ranges. An additional program for catch-up vaccination of 12-year-olds would have high incremental costs if the vaccination coverage rate of children of preschool age were 97%, but would result in net savings at a coverage rate of 50%. CONCLUSIONS: A routine varicella vaccination program for healthy children would result in net savings from the societal perspective, which includes work-loss costs as well as medical costs. Compared with other prevention programs, it would also be relatively cost-effective from the health care payer's perspective.
Evaluation of a method for detecting aberrations in public health surveillance data.
The detection of unusual patterns in routine public health surveillance data on diseases and injuries presents an important challenge to health workers interested in early identification of epidemics or clues to important risk factors. Each week, state health departments report the numbers of cases of about 50 notifiable diseases to the Centers for Disease Control and Prevention, and these reports are published weekly in the Morbidity and Mortality Weekly Report. A new analytic method and a horizontal bar graph were introduced in July 1989 to facilitate easy identification of unusual numbers of reported cases. Evaluation of the statistical properties of this method indicates that the results are fairly robust to nonnormality and serial correlation of the data. An epidemiologic evaluation of the method after the first 6 months showed that it is useful for detection of specific types of aberrations in public health surveillance.
Case definitions for public health surveillance.
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Novel dihydrofolate reductases isolated from epidemic strains of trimethoprim/sulfamethoxazole-resistant Shigella sonnei.
Two strains of trimethoprim-resistant Shigella sonnei bearing R plasmids pBH600 and pBH700 each elaborated a dihydrofolate reductase (DHFR) and were moderately resistant to trimethoprim (minimum inhibitory concentrations, 128 and 256 micrograms/ml, respectively). Neither plasmid hybridized to probes for DHFR types I, II, or III. The trimethoprim resistance genes from the R plasmids resided on a 1600-base pair (bp) PstI fragment of pBH600 and an 1800-bp PstI fragment of pBH700. Isoelectric focusing showed distinct isoelectric points for the enzymes coded for on pBH600 (5.3) and pBH700 (5.6-5.7). Trimethoprim-resistant S. sonnei from 10 locations in nine states were examined. Isolates from 8 locations hybridized only to a pBH700-derived probe and one isolate hybridized to a pBH600-derived probe. These two trimethoprim resistance genes appear novel. The gene on plasmid pBH700 codes for an enzyme that seems widespread among S. sonnei isolates in the USA.