Cough symptoms in children aged 5–14 years in Sydney,Australia: non‐specific cough or unrecognized pertussis?

OBJECTIVE: The aim of this study was to estimate the community prevalence of coughing symptoms, consistent with surveillance definitions for pertussis, and doctor-diagnosed pertussis in children aged 5-14 years. METHODOLOGY: A telephone survey of a cross-sectional community sample of parents regarding their child's cough symptoms in the previous 12 months was undertaken in a representative Australian urban region. RESULTS: In 2020 interviews, parents reported that 22% of children had a cough lasting 2 weeks or longer in the preceding 12 months, and 14% (283) had additional symptoms meeting the Centers for Disease Control (CDC) case definition for pertussis. A cough meeting the case definition was significantly more commonly reported by parents of children aged 5-9 years (17%; P < 0.001) but reported exposure to diagnosed pertussis in such cases was significantly more common in children aged 10-14 years (4.3%; odds ratio 12.8; P < 0.01). Parents of 90% of children meeting the CDC case definition sought medical advice. A diagnosis of pertussis was reported in only 1.2% of cases, which extrapolates to an annual incidence of doctor-diagnosed pertussis of 347/100,000 (95% confidence interval, 140-714 per 100,000). This contrasts with 29/100,000 notified cases in the same age group, time period and geographic area. CONCLUSION: Cough episodes meeting a clinical case definition for pertussis commonly used in surveillance are reported by a high proportion of carers of school-aged children in Australia. The majority of children who met the CDC and Australian case definitions for pertussis and sought medical attention were not identified as potentially having pertussis, suggesting underdiagnosis of pertussis. Even if less than half of this is true pertussis, the potential impact in terms of transmission of pertussis in the community is likely to be high. The reported incidence of doctor-diagnosed disease estimated from this survey was at least five and up to 20 times the official notification rate. More work needs to be done in raising awareness among medical practitioners of pertussis as a differential diagnosis in older children and adolescents with cough.     

A comparison of laboratory and clinical methods for diagnosing pertussis in an outbreak in a facility for the developmentally disabled

During a pertussis outbreak in a facility for the developmentally disabled, culture- or direct fluorescent-antibody-confirmed cases were identified in 24 residents and 17 staff members; 38 (93%) were culture positive for Bordetella pertussis. An enzyme-linked immunosorbent assay (ELISA) was used to detect serum IgG and IgA to the filamentous hemagglutinin and lymphocytosis-promoting factor of B. pertussis. Using criteria from ELISA values, we identified an additional 83 residents and 28 staff members as seropositive. Among seropositive persons, antibody levels were elevated by the time of onset of respiratory symptoms and, in three of the four assays, remained elevated for 14 mo. In 44 seropositive persons tested within two weeks of onset of symptoms, 80% were culture positive, compared with 33% of 15 tested two to four weeks after onset (P = .003) and none of 15 tested more than four weeks after onset. The most specific (94%) clinical case definition identified only 41% of seropositive persons. Thus, ELISAs are important tools for individual diagnosis and epidemiological studies of pertussis.     

Risk Factors for Diagnostic Delay in Achalasia

This study investigates whether the frequentlydelayed diagnosis of achalasia is attributable toatypical symptoms, misleading diagnostic features, orthe number of physicians consulted. Eighty-sevenconsecutive patients with newly diagnosed achalasia wereprospectively investigated with the use of structuredinterviews as well as manometric, endoscopic, andradiographic studies. The mean duration of symptoms was 4.7 ± 6.4 years. Quality and intensityof symptoms had no effect on early diagnosis. Amongdifferent radiographic and manometric features, only thewidth of the gastric cardia showed a significantcorrelation with a delay in diagnosis (P < 0.01).However, the most significant association was foundbetween the duration of symptoms prior to consideringthe diagnosis of achalasia and the number ofunsuccessful physician consultations (P = 0.001). We conclude that thefrequent delay in the diagnosis of achalasia is not dueto an atypical clinical presentation of this disease butrather to misinterpretation of typical findings by the physician consulted.     

Incidence of pertussis in persons < or =15 years of age in Valencia, Spain: seroprevalence of antibodies to pertussis toxin (PT) in children, adolescents and adults

PURPOSE: To determine the incidence of pertussis in persons < or =15 years in age in Valencia, Spain. To assess the prevalence of IgG antibodies to pertussis toxin (PT) in children, adolescents and adults. METHODS: Prospective study conducted at paediatric primary care centres. All persons < or =15 years in age presented with persistent cough were enrolled. Parents completed a brief questionnaire and immunization history was obtained from paediatrician records. A blood sample was obtained, for determination of IgG antibodies to Bordetella pertussis toxin (PT) by an ELISA method. A study confirmed-case was the presence of two conditions: (1) cough illness of > or =14 days duration; and (2) ELISA absorbance value of IgG to PT > or =2. Two subjects per clinical-case (same centre and range of age) and parents were asked to participate in the prevalence study. RESULTS: Sixty-one children < or =15 years in age presented with symptoms leading to a clinical diagnosis of pertussis were detected. Serological evidence of recent pertussis was found in five of these patients (incidence of 46.0/100,000 persons < or =15 years in age). Prevalence of antibodies to B. pertussis (> or =0.3) in children < or =15 years in age and adults was 39 and 33%, respectively. Only a minority of children, adolescents and adults had absorbance values indicative of immunity (> or =1). CONCLUSIONS: These incidence and seroprevalence results show that despite high immunization rates in infancy, B. pertussis is circulating in Spain.     

Frequency of pertussis in children with prolongued cough

To determine the frequency of pertussis in children < or = 16 y who had prolonged cough (> or = 14 d), a prospective study was conducted at an outpatient clinic of a paediatric hospital. Nasopharyngeal swabs were taken for culture and nucleic acid testing by polymerase chain reaction (PCR) for Bordetella pertussis. Immunoglobulin A and immunoglobulin G antibodies against pertussis toxin (PT) were tested by ELISA in paired serum samples. A total of 148 patients were recruited during 1 y. Pertussis was detected in 25 (16.9%) patients with at least 1 of the tests. PCR was positive in 12 patients, and 9 cases was diagnosed serologically. Both PCR and serology were positive in 4 children. Duration of cough was longer in the patients with pertussis (median 33 vs 20, p = 0.03). Seropositivity of pertussis toxin was higher in pertussis negative patients during enrollment (24% vs 65%, p = 0.005). From the results of this study, B. pertussis seems to be common in our population despite high immunization rates with whole cell vaccine. Although the duration of cough is defined as longer than 21 d in some studies for pertussis case definition criteria, it was shorter than this in 3 of our cases.     

Outbreak of pertussis on a college campus

Background

Pertussis is increasing among adolescents and adults despite universal childhood vaccination. This investigation describes an outbreak of pertussis among undergraduate students and assesses the burden of cough illness on a college campus.

Methods

Students presenting with prolonged cough were evaluated with culture, polymerase chain reaction (PCR), and serology. An e-mail survey was performed to determine the burden of cough illness on campus.

Results

Thirty-seven undergraduates were evaluated. Their mean duration of cough was 28 days. No student had cultures positive for B. pertussis; one was PCR positive. Ten (27%) had serologic values consistent with acute pertussis infection. The e-mail survey was returned by 225/500 (45%) students. Of these, 66 (29%; 95% confidence interval [CI], 23%-36%) reported a cough of 2 weeks or longer duration during the fall semester. A conservative estimate showed that the campus-wide incidence of a cough illness meeting the Centers for Disease Control and Prevention case definition for pertussis was 13% (95% CI, 10%-16%) during the fall semester.

Conclusions

Adolescents and young adults are susceptible to pertussis infection. This study demonstrates that there was a substantial rate of pertussis infection during an outbreak on a college campus. Our findings support the routine use of the acellular pertussis vaccine in adolescents and adults.     

Epidemiological features of pertussis in hospitalized patients in Canada, 1991-1997: report of the Immunization Monitoring Program--Active (IMPACT).

To assess the morbidity associated with the continued high levels of pertussis, we studied all children <2 years of age who were admitted to the 11 Immunization Monitoring Program--Active (IMPACT) centers, which constitute 85% of Canada's tertiary care pediatric beds. In the 7 years preceding implementation of acellular pertussis vaccine, a total of 1,082 pertussis cases were reported, of which 49.1% were culture-confirmed. The median age of the patients was 12.4 weeks; 78.9% of cases were in children <6 months of age. Complications of pertussis were common: pneumonia was reported in 9.4% of cases, new seizures in 2.3%, and encephalopathy in 0.5%. There were 10 deaths (0.9%), all in children < or =6 months of age. Duration of hospitalization was longer (9.3 days vs. 4.9 days; P = .001) and intensive care was required more frequently (19.2% vs. 4.9%; P = .001) in infants under <6 months of age than in those > or =6 months. Pertussis continues to cause significant morbidity and occasional mortality in Canada, particularly in young infants.     

Evidence of Bordetella pertussis infection in adults presenting with persistent cough in a french area with very high whole-cell vaccine coverage

Although France has had a vaccination program for 40 years, since 1990, an increase in whooping cough cases with parent-infant transmission has been observed. This study prospectively assessed the frequency of Bordetella pertussis infection in adults who consulted general practitioners for a persistent cough without an evident diagnosis. Among 217 patients, 70 (32%) confirmed whooping cough cases were identified. One case was culture positive, 36 were polymerase chain reaction positive, and 40 had increases or decreases of > or =2-fold in anti-pertussis toxin IgG titer between serum samples collected during the acute and convalescent phases. The median duration of cough in confirmed cases was 49 days (range, 13-123 days). Of the patients, 60% reported vaccination, and 33% reported whooping cough in infancy. Pertussis should be considered for diagnosis of acute and chronic cough in adults. Future studies should evaluate the public health interest of booster doses of pertussis vaccine in adults.     

Identification of Malaria Retinopathy Improves the Specificity of the Clinical Diagnosis of Cerebral Malaria: Findings from a Prospective Cohort Study

The diagnosis of cerebral malaria (CM) is difficult to confirm in endemic regions with limited neurodiagnostics. Accurate diagnoses are critical for trials and outcomes studies. Findings from an autopsy-based study suggest that identifying malaria retinopathy in children satisfying the standard clinical case definition of CM improves our ability to accurately diagnose CM in vivo. In a post hoc analysis of a prospective exposure-control study to evaluate CM as a risk factor for epilepsy, we stratified children meeting the standard case definition by their retinopathy status (presence versus absence) and compared these groups for pre-existing risk factors for epilepsy. We also compared them to the concurrently enrolled, non-comatose controls. Children meeting the standard case definition of CM who lacked malaria retinopathy had a higher prevalence of pre-existing developmental problems and family history of epilepsy. This subset of patients may represent children with a pre-existing propensity to adverse neurologic symptoms and outcomes.     

Factors influencing gender differences in the diagnosis and treatment of asthma in childhood: the Tucson Children's Respiratory Study

Studies identified gender differences in diagnosed asthma, but the extent to which they can be attributed to differences in symptom experience and frequency rather than factors influencing diagnosis has not been established. We investigated prevalence of, and consultation for, asthma symptoms, as well as diagnosis and treatment in 533 boys and 556 girls enrolled in the Tucson Children's Respiratory Study, a population-based birth-cohort study. Questionnaires regarding respiratory symptoms and diagnoses were obtained at ages 2, 3, 6, 8, 11, 13, 16, and 18 years. Boys were significantly more likely than girls to experience both wheeze and frequent wheeze most years in the first decade of life. However, girls with symptoms were less likely than boys to see a physician (74.1% vs. 83.4%, P < 0.001) and to be labeled as having asthma (43.3% vs. 53.8%, P < 0.009), even after adjusting for symptom frequency. A difference in symptom presentation also appeared to influence diagnosis: nocturnal cough without frequent wheeze was more prevalent among girls, and was associated with reduced diagnosis of asthma. Among subjects who consulted a physician for wheeze, boys were significantly more likely than girls to have taken medication (81.5% vs. 73.5%, P < 0.01). The lag time between age at first wheeze and first use of medication among those consulting a physician for wheeze or asthma was greater for girls, especially among subjects with frequent wheeze (2.8 vs. 1.6 years, P < 0.005). These findings indicate that gender differences in the diagnosis and treatment of asthma cannot be explained completely by differences in symptom prevalence and frequency.     

Prevalence and Associated Features of Gastroesophageal Reflux Symptoms in a Caucasian-Predominant Adolescent School Population

OBJECTIVE: To determine the prevalence of esophageal symptoms and associated symptoms of gastroesophageal reflux symptoms in 14-18 year-old high school students and the percentage of symptomatic adolescents who saw a physician or received medications. DESIGN AND SETTING: A cross-sectional questionnaire administered to students at two high schools. PARTICIPANTS: 1,286 completed questionnaires were analyzed. The study sample consisted of 57% Caucasians and 57% males, with a mean age of 15.7 (+/-1.3) years. INTERVENTION: No intervention was used. Participants completed questionnaires only. RESULTS: 714 students (56%) reported at least one esophageal or respiratory symptom. Esophageal symptoms reported were: heartburn (22%), regurgitation (21%), and dysphagia (15%). Respiratory symptoms reported were: shortness of breath (24%), wheezing (20%), and cough (18%). Students with at least one esophageal symptom were more likely to experience at least one respiratory symptom than were students with no esophageal symptoms (52% vs. 25%; p < 0.001). Cigarette, alcohol, and non-steroidal anti-inflammatory drug use were risk factors for both respiratory and esophageal symptoms. Of those experiencing one or more of these symptoms, 4% reported that the symptoms affected their daily activities, 23% visited a physician, and 25% took medication in the past year. CONCLUSIONS: Esophageal symptoms of gastroesophageal reflux are frequent in adolescents. Fewer than 25% of students with gastroesophageal reflux symptoms consulted a physician and/or took medications.     

Patterns of susceptibility in an outbreak of Bordetella pertussis: Evidence from a community-based study.

OBJECTIVE: To describe an outbreak of Bordetella pertussis and to assess which factors were associated with the development of clinical pertussis in children and adults during the outbreak. DESIGN: A case series was described to define the epidemiology of the pertussis outbreak. A school-based survey of children was used to measure the incidence of clinical pertussis over the previous six months. Vaccination records from the local public health facility were used to look at the relationship between age and vaccination parameters, and susceptibility to clinically diagnosed pertussis. A cross-sectional survey of teachers, parents and some hospital workers was used to assess these associations in adults. SETTING: An outbreak of pertussis in an isolated northern community in British Columbia. POPULATION STUDIED: All children in the community who attend daycare, kindergarten or school, and their parents were surveyed. In addition, some health care workers and mothers of preschool children were surveyed. MAIN RESULTS: A total of 31 suspected cases of pertussis were identified over a three-month period. Ninety per cent of the affected children who had available vaccination records had received four or five doses of pertussis vaccine. Sixty per cent of the town's 209 children returned completed surveys. Of these, 69% had available vaccination records. Thirty-six children (28%) reported symptoms that fit the case definition for pertussis over the previous three months. Attack rates were highest for the group of children aged 10 to 14 years. In a multivariate logistic regression analysis, receiving prophylactic medication and an increased number of years from the last vaccine dose were found to be significant predictors for developing pertussis. Thirty-four per cent of the estimated 291 adults in the community returned completed surveys. The attack rate of pertussis in the adults was only 9%. Being a member of the school staff and/or having a household contact with pertussis were significant predictors of developing pertussis. CONCLUSIONS: Immunity to pertussis appears to wane during childhood. Peak susceptibility appears to be during early adolescence. Adults do not seem to be at greater risk than adolescents for developing the disease, but it seems unlikely that this is due to better immunity. Rather, it is probably related to a lower risk of exposure to pertussis and a lower rate of progression to symptomatic disease when adults are infected.     

Clinical definitions of pertussis: Summary of a Global Pertussis Initiative roundtable meeting, February 2011

Existing clinical case definitions of pertussis are decades old and based largely on clinical presentation in infants and children, yet an increasing burden is borne by adolescents and adults who may manifest distinct signs/symptoms. Therefore, a "one-size-fits-all" clinical case definition is no longer appropriate. Seeking to improve pertussis diagnosis, the Global Pertussis Initiative (GPI) developed an algorithm that delineates the signs/symptoms of pertussis most common to 3 age groups: 0-3 months, 4 months to 9 years, and ≥10 years. These case definitions are based on clinical presentation alone, but do include recommendations on laboratory diagnostics. Until pertussis can be accurately diagnosed, its burden will remain underestimated, making the introduction of epidemiologically appropriate preventive strategies difficult. The proposed definitions are intended to be widely applicable and to encourage the expanded use of laboratory diagnostics. Determination of their utility and their sensitivity and/or specificity versus existing case definitions is required.     

Childhood asthma surveillance using administrative data: Consistency between medical billing and hospital discharge diagnoses

BACKGROUND:

The absence of ongoing surveillance for childhood asthma in Montreal, Quebec, prompted the present investigation to assess the validity and practicality of administrative databases as a foundation for surveillance.

OBJECTIVE:

To explore the consistency between cases of asthma identified through physician billings compared with hospital discharge summaries.

METHODS:

Rates of service use for asthma in 1998 among Montreal children aged one, four and eight years were estimated. Correspondence between the two databases (physician billing claims versus medical billing claims) were explored during three different time periods: the first day of hospitalization, during the entire hospital stay, and during the hospital stay plus a one-day margin before admission and after discharge (‘hospital stay ± 1 day’).

RESULTS:

During 1998, 7.6% of Montreal children consulted a physician for asthma at least once and 0.6% were hospitalized with a principal diagnosis of asthma. There were no contemporaneous physician billings for asthma ‘in hospital’ during hospital stay ± 1 day for 22% of hospitalizations in which asthma was the primary diagnosis recorded at discharge. Conversely, among children with a physician billing for asthma ‘in hospital’, 66% were found to have a contemporaneous in-hospital record of a stay for ‘asthma’.

CONCLUSIONS:

Both databases of hospital and medical billing claims are useful for estimating rates of hospitalization for asthma in children. The potential for diagnostic imprecision is of concern, especially if capturing the exact number of uses is more important than establishing patterns of use.     

Morbidity of pertussis in adolescents and adults

The effect of age on the clinical presentation of pertussis was assessed in 664 adolescent and adult cases. Complications were more frequent in adults than in adolescents (28% vs. 16%). Pneumonia occurred in 2% of patients <30 years old but in 5%-9% of older patients. Urinary incontinence occurred in 34% of women >/=50 years old. Duration of cough, risk of sinusitis, and number of nights with disturbed sleep increased with smoking and asthma. The secondary attack rate in other household members >/=12 years was 11%. Pertussis in secondary case patients was less severe than in index case patients but presented with classic symptoms. The main source of infection in adolescents was schoolmates or friends; in adults it was workplace or their children. Teachers and health care workers had a greater risk of pertussis than did the general population. The burden of disease appears to increase with age, with smoking, and with asthma.     

Changing epidemiology of pertussis in the United States: increasing reported incidence among adolescents and adults, 1990-1996.

Since 1990, the reported incidence of pertussis has increased in the United States with peaks occurring every 3-4 years. On the basis of analysis of pertussis cases reported to the Centers for Disease Control and Prevention, the incidence remained stable among children aged younger than 5 years, most of whom were protected by vaccination. In contrast to 1990-1993, during 1994-1996, the average incidence among persons aged 5-9 years, 10-19 years, and 20 years or older increased 40%, 106%, and 93%, respectively. Since 1990, 14 states reported pertussis incidences of > or =2 cases per 100,000 population during at least 4 years between 1990 and 1996; seven of these states also reported that a high proportion of cases occurred in persons aged 10 years or older. Analysis of national data on pertussis did not provide sufficient information to fully elucidate the relative importance of multiple possible explanations for the increase in the incidence of pertussis in adolescents and adults. Improvement in diagnosis and reporting of pertussis in this age group, particularly in some states, is an important factor contributing to the overall increase.     

The diagnostic pathway to sarcoidosis

PURPOSE: To examine the time from the first physician visit to the diagnosis of sarcoidosis. HYPOTHESES: The time required to diagnose sarcoidosis is dependent on the initial symptoms, socioeconomic status, referral to a specialist, race, and severity of pulmonary involvement. METHODS: Patients were recruited from the Case Control Etiology of Sarcoidosis Study (ACCESS) and had biopsy-confirmed sarcoidosis. Subjects were asked to recall the date of onset of symptoms of sarcoidosis, their first physician visit, number of physician visits, and types of physicians seen. RESULTS: One hundred eighty-nine patients were enrolled. The diagnosis of sarcoidosis was made on the first physician visit in only 15.3% of cases. The presence of pulmonary symptoms was associated with prolonged time (> 6 months vs < or = 6 months, p = 0.02) until diagnosis, and the presence of skin symptoms with a shorter time (< or = 6 months vs > 6 months, p = 0.02) until diagnosis. Patients with pulmonary symptoms had more physician visits (mean +/- SEM) until the diagnosis was made compared to those without pulmonary symptoms (4.84 +/- 0.38 visits vs 3.15 +/- 0.24 visits, p = 0.0002). The mean baseline FEV(1) was greater in those diagnosed < or = 6 months from the first physician visit than those diagnosed > 6 months (87.3 +/- 1.52% predicted vs 81.2 +/- 2.5% predicted, p = 0.04). There was a significant delay in diagnosis (> 6 months vs < or = 6 months) from first physician visit with higher Scadding stages (stage 4 vs stage 2, or stage 3 vs stage 0 or 1, p = 0.04). CONCLUSIONS: The diagnosis of sarcoidosis is often delayed and seems to be more a factor of disease presentation than patient or physician characteristics. The presence of pulmonary symptoms or higher radiographic stages is associated with a prolonged time until diagnosis. The presence of skin symptoms is associated with less delay in diagnosis. It is likely that the delay in diagnosis of pulmonary sarcoidosis relates to the fact that pulmonary symptoms and parenchymal involvement are nonspecific and are often regarded as manifestations of other pulmonary diseases.     

Patterns of susceptibility in an outbreak of Bordetella pertussis: Evidence from a community-based study

OBJECTIVE:

To describe an outbreak of Bordetella pertussis and to assess which factors were associated with the development of clinical pertussis in children and adults during the outbreak.

DESIGN:

A case series was described to define the epidemiology of the pertussis outbreak. A school-based survey of children was used to measure the incidence of clinical pertussis over the previous six months. Vaccination records from the local public health facility were used to look at the relationship between age and vaccination parameters, and susceptibility to clinically diagnosed pertussis. A cross-sectional survey of teachers, parents and some hospital workers was used to assess these associations in adults.

SETTING:

An outbreak of pertussis in an isolated northern community in British Columbia.

POPULATION STUDIED:

All children in the community who attend daycare, kindergarten or school, and their parents were surveyed. In addition, some health care workers and mothers of preschool children were surveyed.

MAIN RESULTS:

A total of 31 suspected cases of pertussis were identified over a three-month period. Ninety per cent of the affected children who had available vaccination records had received four or five doses of pertussis vaccine. Sixty per cent of the town''s 209 children returned completed surveys. Of these, 69% had available vaccination records. Thirty-six children (28%) reported symptoms that fit the case definition for pertussis over the previous three months. Attack rates were highest for the group of children aged 10 to 14 years. In a multivariate logistic regression analysis, receiving prophylactic medication and an increased number of years from the last vaccine dose were found to be significant predictors for developing pertussis. Thirty-four per cent of the estimated 291 adults in the community returned completed surveys. The attack rate of pertussis in the adults was only 9%. Being a member of the school staff and/or having a household contact with pertussis were significant predictors of developing pertussis.

CONCLUSIONS:

Immunity to pertussis appears to wane during childhood. Peak susceptibility appears to be during early adolescence. Adults do not seem to be at greater risk than adolescents for developing the disease, but it seems unlikely that this is due to better immunity. Rather, it is probably related to a lower risk of exposure to pertussis and a lower rate of progression to symptomatic disease when adults are infected.Key Words: Immunity, Pertussis, VaccinationVaccination against Bordetella pertussis has resulted in a dramatic reduction in the incidence of this disease in Canada. Outbreaks of pertussis, however, still occur. While many outbreaks reported elsewhere occur in populations where vaccination rates have declined, many others occur in populations with high vaccination coverage (1,2). This has not changed with the introduction of the acellular pertussis vaccine. The reasons for this are not clear, but waning immunity and the transmission of disease from adolescents and adults to younger children have been proposed as possible mechanisms (3,4). An additional constraint in studying this problem is that there is no known level of antibody that can be shown to be protective against developing pertussis (5).The idea of waning immunity has been challenged recently. De Serres and colleagues (6) found that the attack rates were the same in adolescent (12%) and adult (11%) household contacts of pertussis index cases. The authors (6) felt that this similar attack rate was more consistent with a decreasing proportion of susceptible subjects with age and with longlasting immunity. They did not suggest that this immunity comes solely from vaccination, but more likely from subclinical boosting from endemic disease. Clearly, this has implications as to the utility of introducing an adolescent booster dose to reduce further the incidence of disease in the population.In May 2000, an outbreak of pertussis was reported in an isolated northern community in British Columbia. Pertussis outbreaks have been known to occur in three- to five-year cycles in British Columbia. The last such outbreak occurred in 1996 and 1997, and resulted in more than 1100 reported cases. Increased rates of pertussis transmission had already been reported throughout the province since January 2000 (British Columbia Centre for Disease Control, internal report). By mid-May 2000, nearly 400 cases had been reported to the British Columbia Centre for Disease Control. Rates of infection were highest among young adolescents (aged 10 to 14 years), followed by older children (aged seven to nine years). The Northwest Coastal Health Services Society (the region that includes the town of Stewart) was not among those health regions that had previously reported increased numbers of cases.The town of Stewart, which has a population of approximately 500 people, has one health centre for both curative and preventive care, and is more than 150 km from the nearest settlement (excluding the hamlet of Hyder, Alaska, which is only 1.6 km away). There are three schools - a public primary school, a public secondary school and a small, private Christian school. The local health region and the Department of Health Care and Epidemiology at the University of British Columbia initiated an investigation of the pertussis outbreak in Stewart. It was thought that the relative isolation of the community and its small size would allow investigators to see whether immunization status, age and the length of time from the last vaccine dose would significantly affect disease attack rates. It was hoped that vaccination records for most of the town''s children could be verified and then compared with the results of a school-based survey for pertussis-like symptoms. As well, a survey of adults was undertaken to determine whether symptoms also occurred in this susceptible group, and whether this was related to recalled vaccination history. Disease control measures (7), including erythromycin prophylaxis of close contacts of index cases and enhanced surveillance among symptomatic individuals, had already been implemented before the present study was undertaken and were not interrupted during the course of the study.     

Efficacy of acellular pertussis vaccine

An outbreak of pertussis occurred in one room of a residential facility where 19 children aged 5 to 36 months were residing. They were prospectively surveyed to estimate the efficacy of acellular pertussis vaccine. Among the 19 residents, 9 were immunized with acellular pertussis vaccine. Among the 19 residents, 9 were immunized with acellular DTP vaccine and 10 were unimmunized. The spread of pertussis was surveyed bacteriologically and serologically for 2 months. Among the 9 immunized, 7 children acquired the laboratory-confirmed pertussis and 1 of the 7 developed the typical symptoms (whooping or paroxysmal coughing attack lasting for 14 days or more). Among the 10 unimmunized, 7 children acquired the laboratory-confirmed pertussis and 6 of the 7 developed the typical symptoms. There was no difference in the rate of secondary infection (7/9:7/10), but there was a significant difference in the rate of development of the typical symptoms (1/7:6/7 p less than 0.05). The point estimate of protective efficacy of the acellular DTP vaccine against typical pertussis was (6/10 - 1/9)/(6/10) x 100 = 81%. It was concluded from these findings that acellular DTP vaccine could not prevent the infection of Bordetella pertussis, but could prevent the development of the typical symptoms.