The Immunization Monitoring Program Active (IMPACT) prospective five year study of Canadian children hospitalized for chickenpox or an associated complication

BACKGROUND

Varicella vaccine was approved for use in Canada in 1998. A major goal of universal varicella vaccine programs is to reduce severe infection and associated complications. Baseline data are essential against which to judge the effectiveness of routine childhood immunization.

OBJECTIVE

To describe morbidity and mortality among children hospitalized for chickenpox. Methods. From January 1, 1991, to March 31, 1996, chickenpox admissions to 11 pediatric referral centers were actively identified. Patient and illness characteristics were compared for 3 subgroups defined by prior health: healthy; unhealthy but immunocompetent; immunocompromised.

RESULTS

Of 861 cases 488 (56.7%) were healthy, 75(8.7%) were unhealthy and 298 (34.6%) were immunocompromised. The immunocompromised children differed from healthy/unhealthy cases in mean age (6.4 vs. 4.0/4.6 years, respectively, P < 0.0001); median interval from rash onset to admission (2 vs. 5/5 days, P < 0.0001); complication rate (20% vs. 90%/79%; P = 0.001); and rate of acyclovir therapy (98% vs. 24%/39%; P = 0.001). Unhealthy vs. healthy cases had a higher frequency (P < 0.01) of intensive care (13.3% vs. 4.7%), ventilation (9.3% vs. 2.0%) and death (4% vs. 0.2%).

CONCLUSION

These data provide a baseline for morbidity/mortality resulting from chickenpox before varicella vaccine use in Canada.

A cognitive-behavioural, group-based intervention for social anxiety in schizophrenia

OBJECTIVE

The objective of this study was to investigate the efficacy of group-based cognitive-behavioural therapy (CBT) for social anxiety in schizophrenia.

METHOD

Patients with schizophrenia (20) with comorbid social anxiety were randomly assigned to the group-based CBT or wait-list control condition. Pre-, post- and 6-week follow-up ratings included measures of social anxiety and avoidance, mood and quality of life.

RESULTS

The intervention group improved on all outcome measures and the control group showed no change in symptomatology.

CONCLUSIONS

Group-based CBT is effective in treating social anxiety in schizophrenia.

Invasive pneumococcal infections in Canadian children, 1991-1998: implications for new vaccination strategies. Canadian Paediatric Society/Laboratory Centre for Disease Control Immunization Monitoring Program, Active (IMPACT)

We reviewed 2040 consecutive cases of invasive pneumococcal infection that were seen at 11 pediatric centers across Canada during 1991-1998 to determine if such infections could be prevented by new conjugate vaccines. Isolates from 1528 cases were serotyped. Most cases (61.5%) occurred in patients aged >2 years. Underlying medical conditions were present in 23.2% of case patients. Serotypes in the 7-valent conjugate vaccine matched isolates as follows: 85.8% of tested isolates from children aged 6 months to 5 years, but significantly fewer isolates in younger and older children; 72.9% of isolates from non-healthy children, but 83.9% of isolates from previously healthy children; and 95.4% of isolates with high-level penicillin resistance, but only 72.7% of those with intermediate-level resistance. Significant natural variation in the proportion of isolates matching 7-valent vaccines occurred from year to year and among centers. New conjugate vaccines have great potential but their effectiveness and limitations require ongoing study.

Cost of chickenpox in Canada: part I. Cost of uncomplicated cases

OBJECTIVE

The purpose of this study was to assess the direct medical costs and productivity losses associated with uncomplicated chickenpox (no hospitalization) in Canada.

METHODS

A total of 179 otherwise healthy 1- to 9-year-old children with active chickenpox were recruited from schools, day care centers, and physician offices in 5 provinces. Direct medical (physician contacts, medication, and diagnostic tests) and nonmedical (personal expenses including child care) resources expended during the illness were determined by caregiver interview. Productivity losses attributable to the disease were determined by assessing caregiver time lost from work and daily activities. Unit costs for all resources were obtained from sources in 2 provinces, and per-patient treatment costs were determined from the patient, Ministry of Health, and societal perspectives.

RESULTS

From a societal perspective, the per-case cost for children from 1 to 4 years of age and from 5 to 9 years of age was $370.2 and $236.5, respectively. Direct medical costs accounted for 10% of the total costs in both groups. The largest cost driver in patient care was caregiver productivity losses, which amounted to $316.5 in the younger age group and to $182.7 in the older age group. Based on an estimated yearly incidence of 344 656 cases of uncomplicated chickenpox in Canada, the total annual societal burden of the disease can be estimated at $109.2 million, with a cost to the Ministry of Health of $11.2 million.

CONCLUSION

Chickenpox is one of the last common childhood diseases prevalent in Canada, and the uncomplicated disease, despite its rather benign course, imparts a large annual economic burden.

Treatment of severe pertussis: a study of the safety and pharmacology of intravenous pertussis immunoglobulin

BACKGROUND

Pertussis in infants is often severe, resulting in complications and prolonged hospitalization. Treatment is limited to supportive care. Antibiotics do not significantly alter the course of the disease. Therapies directed at pertussis toxin, a major virulence factor of Bordetella pertussis, might be beneficial. This study examines the safety and pharmacology of intravenous pertussis immunoglobulin (P-IGIV), which has high levels of pertussis toxin antibodies.

METHODS

P-IGIV was prepared as a 4% IgG solution from the pooled plasma from donors immunized with inactivated pertussis toxoid. The IgG pertussis toxin antibody concentration of 733 microg/ml is >7-fold higher than contained in conventional intravenous immunoglobulin products. Children with presumptive pertussis were allocated to one of three treatment doses of P-IGIV.

RESULTS

Twenty-six of 30 enrolled children had confirmed pertussis. There were no adverse events associated with P-IGIV except one patient who had transient hypotension that responded to an infusion rate decrease. P-IGIV doses of 1500, 750 and 250 mg/kg achieved > or =4-fold, 3-fold and >2-fold rises in peak geometric mean titers of pertussis toxin IgG antibodies, respectively. P-IGIV exhibited a half-life of 38.4 days and a volume of distribution of 87.8 ml/kg. All three treatment groups showed declines in lymphocytosis (P < 0.05) and paroxysmal coughing by the third day after P-IGIV infusion compared with preinfusion values.

CONCLUSION

P-IGIV is safe and achieves high pertussis toxin antibody titers in infants. This study provides data for a prospective, controlled trial of P-IGIV.

Failure of physicians to consider the diagnosis of pertussis in children

To determine the ability of physicians to make a diagnosis of pertussis and factors associated with improved diagnosis, 8,235 children from 88 child care centers and 14 elementary schools from Quebec City, Quebec, Canada, were evaluated by using a questionnaire completed by parents and a medical record review. Children must have consulted a physician to be included in the evaluation. There were 558 children meeting the surveillance case definition and 416 meeting a modified World Health Organization case definition who consulted a physician. A diagnosis of pertussis was considered in 24%-26% of children meeting either case definition, made in 12%-14%, and reported for 6%. Pertussis diagnosis was significantly associated with having a history of pertussis exposure (P < or = .003), four pertussis-related symptoms (P < .001), and a cough for > or = 5 weeks (P < or = .05) and consulting in a hospital setting (P < or = .03). The proportion of cases of pertussis diagnosed and reported is low even when children present with classical symptoms.

Effectiveness of a whole cell pertussis vaccine in child-care centers and schools

BACKGROUND

Pertussis has substantially increased in Quebec, Canada, since 1990. We estimated pertussis vaccine effectiveness and vaccine coverage in child-care centers and elementary schools.

METHODS

Two retrospective cohort studies were simultaneously conducted. One included 4482 children attending 88 public child-care centers and the other included 3429 pupils in 14 elementary schools. Cough and pertussis symptoms were assessed through a questionnaire and medical records; immunization status was ascertained by examination of written records.

RESULTS

In child-care centers 95% of children had received at least three vaccine doses at the beginning of the follow-up; in schools more than 98% of pupils had received at least 4 doses. With > or = 4 doses of vaccine and a standard case definition used for surveillance (cough > or = 2 weeks, > or = 1 pertussis symptom and no other apparent cause for cough), vaccine effectiveness was estimated at 61% (95% confidence interval, 44 to 72%) in child-care centers and at 60% (95% confidence interval, 10 to 82%) in schools. With the same number of doses but a case definition requiring a cough > or = 5 weeks, vaccine effectiveness increased to 71% (95% confidence interval, 49 to 83) in child-care centers and to 86% (95% confidence interval, 66 to 94%) in schools.

CONCLUSIONS

The increase in pertussis in Quebec is not caused by a low vaccine coverage. A low vaccine effectiveness may contribute to the resurgence of pertussis in the past decade.

Clinical course of pertussis in immunized children

To describe the clinical course of Bordetella pertussis infection in a highly immunized childhood population, we studied prospectively endemic and epidemic pertussis in a metropolitan population with an immunization rate > 90% during an 8-year period from 1987 through 1994. Patients with a possible diagnosis of pertussis were referred by family or emergency room physicians for nasopharyngeal culture. Patients with a culture positive for B. pertussis were contacted by a nurse who completed a detailed questionnaire for the index case and all family members. Repeat home visits were made each week for 4 weeks. Of the 189 patients with pertussis who were evaluated 103 subjects were < 5 years of age. Congestion predated the onset of cough by up to 1 week in 35 (34%) cases. Seventy (68%) subjects < 5 years of age developed a paroxysmal cough within the first week of their illness. Ninety-one (88%) cases < 5 years old had a persistent paroxysmal cough for > 21 days. Coughing in this group lasted from 16 to 91 days (median 48). Erythromycin therapy appeared to shorten the duration of cough; however, patients were not randomized to receive erythromycin at a specific time. Despite adequate immunization some children develop pertussis. The clinical course in these patients is milder than in unimmunized subjects. Nevertheless the symptomatology in these children should still be readily identified by most physicians using classical clinical criteria of pertussis.

Stress and unaided smoking cessation: a prospective investigation

A prospective design was used to determine the outcomes associated with unaided smoking cessation and the influence of stress on cessation. Heavy smokers (N = 308) completed stress-related measures and were then recontacted at 1, 6, and 12 months. At each follow-up, they indicated their smoking status (which was confirmed by collateral report and biochemical tests) and completed several stress-related questionnaires. Results indicated that 33% of subjects smoked continuously throughout the year, 39% quit briefly but subsequently relapsed, and 15% quit (confirmed biochemically). An additional 7% reported that they had quit, but this could not be confirmed, and 6% were lost to follow-up. Compared with nonquiters, quitters reported less perceived stress, greater self-efficacy, greater use of problem solving and cognitive restructuring, and less reliance on wishful thinking, self-criticism, and social withdrawal. A model to forecast quitting was built and cross-validated.

Stress and unaided smoking cessation: a prospective investigation

A prospective design was used to determine the outcomes associated with unaided smoking cessation and the influence of stress on cessation. Heavy smokers (N = 308) completed stress-related measures and were then recontacted at 1, 6, and 12 months. At each follow-up, they indicated their smoking status (which was confirmed by collateral report and biochemical tests) and completed several stress-related questionnaires. Results indicated that 33% of subjects smoked continuously throughout the year, 39% quit briefly but subsequently relapsed, and 15% quit (confirmed biochemically). An additional 7% reported that they had quit, but this could not be confirmed, and 6% were lost to follow-up. Compared with nonquiters, quitters reported less perceived stress, greater self-efficacy, greater use of problem solving and cognitive restructuring, and less reliance on wishful thinking, self-criticism, and social withdrawal. A model to forecast quitting was built and cross-validated.

Deficient priming activity of newborn cord blood-derived polymorphonuclear neutrophilic granulocytes with lipopolysaccharide and tumor necrosis factor-alpha triggered with formyl-methionyl-leucyl-phenylalanine

Newborn infants are more susceptible to bacterial infections than adults. This susceptibility has been attributed to defects in humoral and cellular activity. Host cellular activity can be modified by factors produced by bacteria or the host in response to infection. We assessed the effect of two factors associated with gram-negative bacterial infection, lipopolysaccharide (LPS) and TNF-alpha, on polymorphonuclear neutrophilic granulocytes (PMN) obtained from adult or newborns (umbilical cord blood). PMN were primed in vitro with LPS (10 micrograms/L) or TNF-alpha (10(-9) M) for 45 min and then assessed, using a chemiluminescence (CL) assay as an indicator of oxidative radical production with formyl-methionyl-leucyl-phenylalanine as the trigger for CL initiation. CL activity of unprimed PMN was similar for adults and newborns (13.3 and 13.7 CL units, respectively). After priming with LPS, CL activity was increased to 43.4 CL units for PMN from adults but to only 17.6 CL units for PMN from newborns (p < 0.001, adults versus newborn increment). Priming of PMN with LPS was most effective when autologous plasma was present. Using FITC-conjugated LPS and a flow cytometry assay, we could demonstrate no difference between the binding affinity of LPS for adult and newborn PMN. However, formyl-methionyl-leucyl-phenylalanine binding studies indicated that adult PMN had a higher number of binding sites. TNF-alpha priming of newborn PMN was also ineffective. Adult PMN increased CL activity by 3.9-fold when primed with TNF-alpha, whereas newborn PMN increased by only 1.75-fold (p < 0.005). This priming deficiency was not attributable to TNF-alpha receptors because phycoerythrin-conjugated TNF-alpha was associated with PMN from adults and newborns equally. Thus, PMN from newborns are not primed effectively in vitro with LPS or TNF-alpha. This defect may contribute to neonatal susceptibility to bacterial infection.

Prolonged survival of Bordetella pertussis in a simple buffer after nasopharyngeal secretion aspiration

A simple method for recovery of Bordetella pertussis is described using phosphate-buffered saline containing a casein hydrolysate for transporting secretions collected by nasopharyngeal aspirate. Bordetella pertussis was reisolated from 92% of clinical specimens held at 4 degrees C for 1 week and from all specimens held at -20 degrees C. This method will facilitate the centralization of laboratory facilities for the diagnosis of pertussis.

Spurious correlations--causes and cures

Although the Pearson Product--Moment Correlation Coefficient is one of the most widely used statistics in the health and behavioral sciences, it is not always appreciated that the critical assumption of bivariate normality underlies its interpretation. When variables have marginal distributions which are skewed or have heavy tails which produce outliers, correlations may be either spuriously large or small. Having diagnosed problems through exploratory data analysis, one must take the appropriate corrective action, such as re-expressing (transforming) variables or selectively discarding discordant observations.