Burden of Children Hospitalized With Pertussis in Canada in the Acellular Pertussis Vaccine Era, 1999-2015

BACKGROUND

Recent increases in pertussis morbidity and mortality rates among young infants have led to a recommendation in some countries for vaccination against pertussis during pregnancy. Having data on the burden of pediatric pertussis in a large population over time is important for establishing the true burden of disease in the acellular pertussis (aP) vaccine era. Here, we describe age-specific epidemiology and morbidity and mortality rates in children hospitalized with pertussis over 17 years across Canada in the aP vaccine era.

METHODS

Patients aged ≤16 years who were admitted to 1 of 12 pediatric tertiary-care hospitals across Canada between 1999 and 2015 with confirmed (laboratory-confirmed or epidemiologically linked) or probable (clinically diagnosed) pertussis were included.

RESULTS

Overall, 1402 patients with pertussis were included. Infants aged <2 months had the highest mean annual incidences of pertussis hospitalization and intensive care unit (ICU) admission (116.40 [95% confidence interval (CI), 85.32-147.49] and 33.48 [95% CI, 26.35-40.62] per 100 000 population, respectively). The overall proportion of children who required ICU admission was 25.46%, and the proportion was highest in infants aged <2 months (37.90%). Over the span of this study, 21 deaths occurred. Age of <16 weeks, prematurity, encephalopathy, and a confirmed pertussis diagnosis were independent risk factors for ICU admission. Age of <4 weeks, prematurity, and female sex were independent risk factors for death.

CONCLUSIONS

In the aP vaccine era, endemic pertussis still contributes considerably to childhood morbidity and death, particularly in infants aged <2 months. Vaccination against pertussis during pregnancy has the potential to reduce this disease burden.

Clinical Profile of Critical Pertussis in Children at a Pediatric Intensive Care Unit in Northern India

Objective

To delineate the clinical profile, complications, intensive care needs, and predictors of mortality in children with critical pertussis.

Methods

Retrospective analysis of case records of children in the pediatric intensive care unit of a tertiary-care hospital, with a diagnosis of critical pertussis over 3 years. Diagnostic criteria included CDC case definition and confirmation by polymerase chain reaction (PCR), when available. Survivors and nonsurvivors were compared to identify predictors of mortality.

Results

36 records were analysed, most cases were infants (31, 86.1%). 10 (27.7%) were (below 6 weeks of age). In the rest, 16 (61.5%) were partially immunized or unimmunized against pertussis. Rapid breathing (88.9%), paroxysmal cough (86.1%) and apnea (41.7%) were common presenting complaints. Hypoxemia (97.2%), hyperleukocytosis (61.1%) and encephalopathy (52.8%) were common complications. Intensive care needs were mechanical ventilation in 11 (30.6%), vasoactive support in 7 (19.4%) and exchange transfusion in 3 (8.3%). Female gender, apnea, hyperleukocytosis, encephalopathy, need for vasoactive support, and mechanical ventilation predicted mortality.

Conclusion

Pertussis demands attention due to its varied presentation, increased complications and higher mortality.

Vaccine-driven virulence evolution: consequences of unbalanced reductions in mortality and transmission and implications for pertussis vaccines

Many vaccines have heterogeneous effects across individuals. Additionally, some vaccines do not prevent infection, but reduce disease-associated mortality and transmission. Both of these factors will alter selection pressures on pathogens and thus shape the evolution of pathogen virulence. We use a mathematical modelling framework to show that (i) the balance of how vaccines reduce transmission versus mortality and (ii) individual variability in protection conferred both shape the evolution of pathogen virulence. Epidemiological (burden of disease) and evolutionary (pathogen virulence) outcomes are both worse when vaccines confer smaller reductions in transmission than in mortality. Furthermore, outcomes are modulated by variability in vaccine effects, with increased variability limiting the extent of virulence evolution but in some cases preventing eradication. These findings are pertinent to current concerns about the global resurgence of pertussis and the efficacy of pertussis vaccines, as the two classes of these vaccines may reduce disease symptoms without preventing infection and differ in their ability to reduce transmission. Furthermore, these findings point to the importance of generating precise predictions for virulence evolution in Bordetella pertussis (and other similar pathogens) by incorporating empirical characterizations of vaccine effects into models capturing the epidemiological details of this system.

Pertussis epidemiological pattern and disease burden in Brazil: an analysis of national public health surveillance data

Objective: We described pertussis epidemiological trends in Brazil between 2010 and 2015. We also assessed tetanus, diphtheria and acellular pertussis (Tdap) vaccine coverage among pregnant women from 2014, the year of the introduction of Tdap maternal immunization recommendation in Brazil, to 2016.Methods: Epidemiological data for incidence, prevalence, hospitalization, mortality, and maternal vaccination coverage were calculated based on the Brazilian public surveillance databases.Results: The epidemiological data analysis results showed that the pertussis average incidence rate (IR) was 2.19/100,000 inhabitants for all ages, with a peak in 2014 (4.03/100,000 inhabitants) and highest incidence in <1-year-old children (IR = 175.20/100,000). 97.6% of pertussis deaths (405/415) were in <1-year-old children. Maternal immunization coverage was 9.2% in 2014, 40.4% in 2015, and 33.8% in 2016.Conclusions: Pertussis incidence and pertussis-related deaths increased in Brazil from 2010 to 2014 and decreased in 2015. In the two years, 2015 and 2016 that followed the NIP recommendation, Tdap vaccination coverage of pregnant women was low and varying from region to region. More efforts and national plans would help increase awareness and maternal immunization coverage.

Severe pertussis infection: A clinicopathological study

We aimed to investigate the clinicopathological features of pertussis in children admitted to a tertiary-care university hospital in Brazil.This was a retrospective cohort study of all pediatric hospital admissions with pertussis from January 1, 2008 to December 31, 2014. We also reported the autopsy findings in children who died.Fifty-five patients admitted to the hospital over the study period had laboratorial confirmation of Bordetella pertussis infection, 17 (30.9%) needed pediatric intensive care unit (PICU) admission and 6 (10.9%) died. All patients who died were younger than 60 days old and unvaccinated for pertussis; 50% of them had coinfection with respiratory syncytial virus. Leukocyte count ≥40,000/mm at hospital admission was an independent risk factor for PICU admission. Mean heart rate during hospitalization ≥160 bpm was an independent risk factor for death. A cut-off point of 41,200 leukocytes/mm at hospital admission had sensitivity of 64.7% and specificity of 89.5% to predict PICU admission (area under the curve 0.75) and sensitivity of 100% and specificity of 81.6% to predict death (area under the curve 0.93). Autopsy showed medial thickening of small pulmonary arteries in 80% of patients who had pulmonary hypertension; intravascular aggregates of leukocytes or pulmonary thrombosis were not observed. Immunohistochemical staining of tissue samples obtained at autopsy identified B pertussis and respiratory syncytial virus in pulmonary and extra-pulmonary sites.Marked leukocytosis at presentation was associated with morbidity and mortality in children hospitalized with pertussis. Implementation of preventive strategies is crucial to diminish the incidence of the disease, especially in young unimmunized infants.

What Pertussis Mortality Rates Make Maternal Acellular Pertussis Immunization Cost-Effective in Low- and Middle-Income Countries? A Decision Analysis

BACKGROUND

 Despite longstanding infant vaccination programs in low- and middle-income countries (LMICs), pertussis continues to cause deaths in the youngest infants. A maternal monovalent acellular pertussis (aP) vaccine, in development, could prevent many of these deaths. We estimated infant pertussis mortality rates at which maternal vaccination would be a cost-effective use of public health resources in LMICs.

METHODS

 We developed a decision model to evaluate the cost-effectiveness of maternal aP immunization plus routine infant vaccination vs routine infant vaccination alone in Bangladesh, Nigeria, and Brazil. For a range of maternal aP vaccine prices, one-way sensitivity analyses identified the infant pertussis mortality rates required to make maternal immunization cost-effective by alternative benchmarks ($100, 0.5 gross domestic product [GDP] per capita, and GDP per capita per disability-adjusted life-year [DALY]). Probabilistic sensitivity analysis provided uncertainty intervals for these mortality rates.

RESULTS

 Infant pertussis mortality rates necessary to make maternal aP immunization cost-effective exceed the rates suggested by current evidence except at low vaccine prices and/or cost-effectiveness benchmarks at the high end of those considered in this report. For example, at a vaccine price of $0.50/dose, pertussis mortality would need to be 0.051 per 1000 infants in Bangladesh, and 0.018 per 1000 in Nigeria, to cost 0.5 per capita GDP per DALY. In Brazil, a middle-income country, at a vaccine price of $4/dose, infant pertussis mortality would need to be 0.043 per 1000 to cost 0.5 per capita GDP per DALY.

CONCLUSIONS

 For commonly used cost-effectiveness benchmarks, maternal aP immunization would be cost-effective in many LMICs only if the vaccine were offered at less than $1-$2/dose.

Association of BCG, DTP, and measles containing vaccines with childhood mortality: systematic review

OBJECTIVES

 To evaluate the effects on non-specific and all cause mortality, in children under 5, of Bacillus Calmette-Guérin (BCG), diphtheria-tetanus-pertussis (DTP), and standard titre measles containing vaccines (MCV); to examine internal validity of the studies; and to examine any modifying effects of sex, age, vaccine sequence, and co-administration of vitamin A.

DESIGN

 Systematic review, including assessment of risk of bias, and meta-analyses of similar studies.

STUDY ELIGIBILITY CRITERIA

 Clinical trials, cohort studies, and case-control studies of the effects on mortality of BCG, whole cell DTP, and standard titre MCV in children under 5.

DATA SOURCES

 Searches of Medline, Embase, Global Index Medicus, and the WHO International Clinical Trials Registry Platform, supplemented by contact with experts in the field. To avoid overlap in children studied across the included articles, findings from non-overlapping birth cohorts were identified.

RESULTS

 Results from 34 birth cohorts were identified. Most evidence was from observational studies, with some from short term clinical trials. Most studies reported on all cause (rather than non-specific) mortality. Receipt of BCG vaccine was associated with a reduction in all cause mortality: the average relative risks were 0.70 (95% confidence interval 0.49 to 1.01) from five clinical trials and 0.47 (0.32 to 0.69) from nine observational studies at high risk of bias. Receipt of DTP (almost always with oral polio vaccine) was associated with a possible increase in all cause mortality on average (relative risk 1.38, 0.92 to 2.08) from 10 studies at high risk of bias; this effect seemed stronger in girls than in boys. Receipt of standard titre MCV was associated with a reduction in all cause mortality (relative risks 0.74 (0.51 to 1.07) from four clinical trials and 0.51 (0.42 to 0.63) from 18 observational studies at high risk of bias); this effect seemed stronger in girls than in boys. Seven observational studies, assessed as being at high risk of bias, have compared sequences of vaccines; results of a subset of these suggest that administering DTP with or after MCV may be associated with higher mortality than administering it before MCV.

CONCLUSIONS

 Evidence suggests that receipt of BCG and MCV reduce overall mortality by more than would be expected through their effects on the diseases they prevent, and receipt of DTP may be associated with an increase in all cause mortality. Although efforts should be made to ensure that all children are immunised on schedule with BCG, DTP, and MCV, randomised trials are needed to compare the effects of different sequences.

[Pertussis in Poland in 2009]

In 2009, 2 390 cases of pertussis were reported in Poland. The incidence 6.3 per 100 000 was higher, 9.5% more compared to the last year (5.7). Highest incidence 38.1 per 100 000 population was observed in 3 years old children and like last year in 10-14 age group (34.7) and among urban areas population. Of 2 390 cases 1079 (45%) were hospitalized. In 2009 no death attributed to pertussis was reported.

Who gives pertussis to infants? Source of infection for laboratory confirmed cases less than 12 months of age during an epidemic, Sydney, 2009

An important approach to protecting infants against pertussis is to provide a booster vaccination to close contacts, however this strategy requires a good understanding of infection sources to be effective. The objective of this study was to identify the most important sources of transmission of pertussis infection to infants, regardless of hospitalisation status. Standardised interviews were conducted during routine follow-up calls with the parent or guardian of laboratory confirmed pertussis cases less than 12 months of age notified to 3 Sydney metropolitan public health units during a pertussis outbreak from January to May 2009. All contacts with a coughing illness or laboratory confirmed pertussis during the 3 weeks prior to onset of illness in the index case, were recorded. A source of infection could not be identified for 29 infants (31%) and a total of 86 known or suspected sources were identified for the other 66 infants. The most frequently identified sources were siblings (36%) and parents (24%), followed by other family members (21%), friends (13%), and settings outside the home such as medical centres (6%). Of 20 siblings aged 3 or 4 years, 16 (80%) were sources of infection, compared with 14 of the 44 (32%) other siblings less than 18 years of age. During this epidemic siblings were more important sources of infant infection than parents. Siblings aged 3 and 4 years of age were particularly important transmitters of pertussis infection to infants. Minimising pertussis infection in 3 and 4 year olds may be an important measure to prevent infant infection.

[Malignant pertussis: an underdiagnosed illness]

PURPOSE

Malignant pertussis is a rare life-threatening illness characterized by severe respiratory failure, severe leukocytosis, and pulmonary hypertension. The purpose of this study was to determine the prevalence of malignant pertussis in infants admitted to a pediatric intensive care unit (PICU) for severe acute respiratory failure associated with severe leukocytosis.

METHODS

This retrospective study was based on review of the medical charts of infants aged less than 3 months admitted to the PICU between 2006 and 2008 for severe acute respiratory failure requiring mechanical ventilation with leukocytosis greater than 50,000/mm3. Clinical and laboratory data were collected. Polymerase chain reaction (PCR) for detection of Bordetella pertussis was performed on nasopharyngeal washes (NPW) stored at -70 degrees C.

RESULTS

Ten patients meeting inclusion criteria were identified. Median age was 2.1 months (range, 0.6 - 3). None of the infants had been vaccinated against pertussis. Although PCR for pertussis was positive in all ten cases, presumptive diagnosis was made in only 3 patients during hospitalization. Nine patients died within a mean of 4.7 +/- 3.3 days after admission. The cause of death was refractory shock and hypoxemia in all cases. Only one patient survived.

CONCLUSION

Malignant pertussis is a severe disease that is almost always fatal. It was underdiagnosed in our PICU. Use of PCR for detection of B. pertussis, i.e., the reference method, should be promoted in developing countries.

[Pertussis in Poland in 2008]

In 2008, 2 163 cases of pertussis were reported in Poland. The incidence 5.7 per 100 000 was higher, 9% more compared to the last year (5.2). Highest incidence 37.7 per 100 000 population was observed in 10 - 14 age group and among urban areas population in all age groups. Of 2163 cases 870 (40%) were hospitalized. In 2008 one death attributed to pertussis was reported.

Collaborative pediatric critical care research network: looking back and moving forward

OBJECTIVE

To update the pediatric critical care community on the progress of the Collaborative Pediatric Critical Care Research Network and plans for the future.

SETTING

The six sites, seven hospitals of the Collaborative Pediatric Critical Care Research Network.

RESULTS

From the time of its inception in August 2005, the Network has engaged in a number of observational and interventional trials, several of which are ongoing. Additional studies are in the planning stages. To date, these studies have resulted in the publication of six manuscripts and five abstracts, with five additional manuscripts accepted and in press.

CONCLUSION

The Network remains committed to its stated goal "to initiate a multicentered program designed to investigate the safety and efficacy of treatment and management strategies to care for critically ill children, as well as the pathophysiologic basis of critical illness and injury in childhood."

[Adult pertussis poses a severe risk for infants]

In Israel, there have been increasing reports of Bordetella pertussis infection among adolescents and adults, but the peak incidence and highest mortality occur among infants. The authors report four cases involving the likely transmission of pertussis from parents to their offspring in two hospitals in Israel. The adoption of proper infection control measures and targeted screening of parents may reduce the potential risk for such transmission.

[Pertussis in 2006]

In 2006 number of reported cases of pertussis in Poland was 1520, 21% less then in the previous year (1925 in 2005). Slightly higher incidence was among females (846 cases, 4,3/100 000) than among males (674 cases, 3,7/100 000). In urban areas incidence was significantly higher 1185 cases (5,1/100 000) than in the rural ones 335 (2,3/100 000). Incidence in urban areas was higher in all age groups. In general number of cases reported in Poland remains relatively low. Problem is uneven distribution in different voivodeships (districts) which bring strong possibility of very low sensitivity of surveillance in some regions.

Pertussis requiring intensive care

OBJECTIVES

To describe children with pertussis who require intensive care.

DESIGN, SETTING AND PATIENTS

An audit in Auckland, New Zealand, of pertussis admissions to the national paediatric intensive care unit (PICU) from 1991 to 2003.

RESULTS

72 children, 97% of whom were <12 months old. The annual number of cases increased with time (p = 0.04). Forty patients (56%) were coughing for less than 8 days before admission. Apnoea or paroxysmal cough was present in 33 (83%) of these children. Thirty five (49%) received assisted ventilation. Four died. 19% were readmitted to PICU. Those readmitted presented with more atypical disease and had a shorter first admission but longer total PICU admission (9 vs 5 days, p = 0.009). Of the 58 children from Auckland, nine either died (three) or had subsequent respiratory or neurodevelopmental problems (six). There was an increased risk (relative risk, 95% CI) of death or disability associated with having a co-morbidity (RR = 5.56, 1.50 to 8.15), an elevated lymphocyte count (RR = 5.75, 1.54 to 13.65), presenting with seizures/encephalopathy (4.87, 1.18 to 8.34) or shock (6.50, 1.89 to 8.94), having a PIM score of 1% or more (RR = 6.20, 1.22 to 21.72), any abnormal neurological signs (RR = 9.65, 3.32 to 15.23) or being readmitted to PICU (RR = 4.63, 1.44 to 8.82).

CONCLUSIONS

Apnoea and paroxysmal cough are key symptoms of pertussis in those with shorter cough duration. Death or disability are frequent. Clinical factors define children at increased risk of these poor outcomes. Early discharge from PICU is associated with an increased risk of readmission and poor outcome.

Qui faut-il vacciner contre la coqueluche ?

Whooping-cough is one of the rare diseases for which vaccine prevention has been available for many years. However, in spite of good vaccine coverage in the infant, the pertussis infection remains a frequent disease in the teenagers and adults partially immunized. The missing diagnosis of the infection, added to its often clinical banal expression, contributes to support the circulation of Bordetella pertussis and explains the contamination of the young infants in whom the disease remains a true danger as the few declared deaths show it every year. Control of the disease must go through reinforcement of vaccination as a practitioner of booster vaccine in preadolescents, teenagers and adults. Instituted since 1998 in the French vaccine calendar, the 2nd booster in preadolescence between 11-13 years olds or 5th dose of vaccine is not enough carried out and must be encouraged like the installation of another additional vaccine dose for adults and certain professional categories. The protection of infants too young to have received the 3 doses goes through the vaccination of their entourage, family and socio-professional alike. The new recommendations thus preach to begin vaccination in children from the age of 2 months, a reinforcement of the vaccine boosters in preadolescents, in adults likely to become parents and in the medical and paramedical personnel in contact with very young infants.

The case for maternal vaccination against pertussis

Despite high vaccine coverage, the incidence of pertussis is increasing in a number of countries. Particularly alarming is the increase of pertussis in infants too young to be (fully) vaccinated, because the highest morbidity and mortality is observed in this category. Maternal vaccination offers the possibility to protect infants from birth until immunity is induced by active vaccination, and has been shown to be effective and safe for tetanus over long periods of time. Maternal vaccination studies with whole-cell pertussis vaccines have not shown serious adverse effects in mother and child. In one study, protection of newborn babies was found. Additional support for the efficacy of maternal vaccination comes from studies showing that transfer of antibodies confers protection against pertussis. Maternal vaccination might be an effective way to decrease morbidity and mortality caused by pertussis in newborn babies.

EPIREVIEW. Pertussis in New South Wales, 1993-2005: the impact of vaccination policy on pertussis epidemiology

OBJECTIVE

To assess whether changes in vaccination policy have affected the epidemiology of pertussis in NSW between 1993 and 2005.

METHODS

Surveillance data from the NSW Notifiable Diseases Database was reviewed for the period.

RESULTS

35,695 cases of pertussis were notified; annual incidence rates varied from 18.4 to 84.2 per 100,000 people. The highest rates of pertussis were consistently found in infants aged 0-6 months. Rates of disease in other age groups changed markedly over the study period, with high rates currently observed in adult age groups.

CONCLUSIONS

New strategies may be needed to control pertussis in infants and in adults who now comprise the largest proportion of cases.

[Pertussis in 2005]

In 2005 number of reported cases of pertussis in Poland was 1925, 35% les then in the previous year (2954 in 2004). More cases occurred among females (1084 cases, 5.5 /100,000) than among males (841 cases, 4.6 /100,000) and in urban areas 1447 (6.2 /100,000) than in the rural ones 478 (3.2 /100,000). But in younger age groups 0-4 and 5-9 higher incidence was observed in rural areas. The difference was particularly big among children les than 1 year. In general number of cases reported in Poland remains relatively low. Problem is uneven distribution in different voivodeships (districts) which bring strong possibility of very low sensitivity of surveillance between regions.

[Morbidity and mortality of infectious diseases determined mass vaccination in children under 5 ans in Bamako District]

Available facts on morbidity and mortality due to PEV diseases for children under 5 years come from routine facts in Bamako District. The Present study through population investigation proposed to evaluate indicators. It was about a transversal investigation realised about 1014 children less than 5 year living in Bamako (on October 2000). The selection of children has been made by boring after stratification of the district based on socio-economic level and stabilization of population of different sectors. According to study, the global incidence rate of target patients of PEV is about 4.93% +- 1.33%. These rate were about 4.14% +- 1.22% for measles which is the 1st cause of morbidity among target patients of PEV, 0.69% +- 0.50% for whooping cough, 0.903% +- 0.19 for poliomyelitis and 0% for neo natal tetanus. For tuberculosis of which evolution have been appreciated trough counting of antituberculosis clinic register (DAT) during 10 years (1990-1999), its tendency was increasing. The death rate registered during investigation was related to measles with an estimated rate of 4.93% +- 4.31%. Results analysis, global incidence of PEV target patients was in decrease at Bamako district. At vaccinated patients against measles (64.3%) and whooping cough (57.14%) is in favour for an investigation about effective vaccinal.

Epidemiological characteristics of pertussis in Vojvodina

Introduction. In the preimmunization era, pertussis was one of the most common respiratory diseases in children in Vojvodina. Material and methods. This paper deals with effects of immunization against pertussis in Vojvodina and its epidemiological characteristics during the last 10 years. Results and discussion. The average incidence rate for the preimmunization era (1948-1960) was 122/100.000. During the period of immunization, the incidence rate has been continuously declining. During the period from 1995 till 2004, average incidence rate was 0,2/100.000 There were 125 registered deaths caused by pertussis in the preimmunization era, and 13 deaths in the immunization period. The last case of death caused by pertussis occurred in 1970. Pertussis vaccination coverage in Vojvodina has been above 95% for a long period of time. Pertussis is still reported, mostly in individual cases. Since 2003, it was registered in children younger than 24 months. During the last decade, 82% of cases were unimmunized children. The majority of affected were infants (59%) and children from 12 to 24 months of age (15%). Pertussis is registered in small children due to delayed immunization and in school children due to loss of immunity. Conclusion. Favorable epidemiological situation of pertussis in Vojvodina is the result of high immunization coverage. The disease is most frequently registered in individual cases, in unimmunized infants and small children. Mild cases of pertussis remain unrecognized in older age groups, in previously immunized children. It is necessary to improve surveillance and laboratory diagnostics of pertussis in order to monitor the epidemiological situation and to provide timely investigation and control of pertussis. .

How increased pertussis vaccination coverage is changing the epidemiology of pertussis in Italy

The epidemiology of pertussis in Italy is described by using data from the statutory notification system and from seroepidemiology studies. Starting from the 1990s, the incidence of pertussis in Italy has shown a sharp decline and is now at the lowest level ever reached. During this time period vaccination coverage has increased from 88% in 1998 to 95% in 2003. In 1996-97, the prevalence of subjects with levels of IgG antibodies against PT greater than 2EU/ml was 77.6%. The increase in vaccination coverage will probably change the pattern of disease transmission and increase the number of susceptible adults, unless administration of booster doses to adolescents and adults is considered.

[Whooping cough is life-threatening for small children. Generous prophylaxis and contact tracing reduce the risks]

The article presents clinical features of pertussis in older children and adults as well as in unvaccinated infants, with the aim to increase the awareness of the disease and to promote implementation of chemoprophylaxis in households with infants. The national routines for reporting according to the Communicable Diseases Act are outlined, contact-tracing around cases of pertussis being mandatory since July 2004.

[Pertussis: its evolution in Argentina at the end of the twentieth century]

The objective of this study was to analize data of pertussis morbidity and mortality in Argentina and vaccination coverage with combined pertussis vaccine (DwPT), which was available from 1969 until 2000 inclusive, and to investigate their interrelation. A retrospective study was performed based on National Registers. Notification and mortality annual mean variation rates and geometric mean rates, by periods, were analyzed, and correlation coefficients between each one of them and with vaccination coverage were calculated. Notification annual mean variation rates for 1969-2000 were -14.34 and for 1980-2000 -17.26; mortality annual mean variation rates for 1980-2000 was -10.41. Vaccination coverage in infants up to one year of age (3 doses) was 44.4% in 1980; less than 60% until 1982 and higher than 80% after 1990. A highly significant inverse correlation was observed, between (a) vaccine implementation, increase in its coverage, introduction of a fifth vaccine dose, and (b) notification and mortality rates. It was observed during the study, that in our country there is a relatively little knowledge about disease occurrence in adults, and an apparent absence of population-based studies performed on the efficacy of erythromycin chemo prophylaxis in epidemics outbreaks. Based on these data, strategies for a better surveillance and control of pertussis, are exposed.

Immune response modulation to DPT vaccine by aqueous extract of Withania somnifera in experimental system

Immunopotentiation on oral feeding of standardized aqueous extract of Withania somnifera (Linn. Dunal, Family Solanaceae) was evaluated in laboratory animals immunized with DPT (Diphtheria, Pertussis, Tetanus) vaccine. The immunostimulation was evaluated using serological and hematological parameters. Treatment of immunized animals with test material (100 mg/kg/day) for 15 days resulted in significant increase of antibody titers to B. pertussis (P=0.000007). Immunized animals (treated and untreated) were challenged with B. pertussis 18,323 strain and the animals were observed for 14 days. Results indicate that the treated animals did show significant increase in antibody titers as compared to untreated animals after challenge (P=0.000003). Immunoprotection against intracerebral challenge of live B. pertussis cells was evaluated based on degree of sickness, paralysis and subsequent death. Reduced mortality accompanied with overall improved health status was observed in treated animals after intracerebral challenge of B. pertussis indicating development of protective immune response. Present study indicates application of the test material as potential immunopotentiating agent possible applications in immunochemical industry. The test material also offers direct therapeutic benefits resulting in reduced morbidity and mortality of experimental animals.

Infant pertussis deaths and the management of cardiovascular compromise

Infants infected with Bordetella pertussis in the first few weeks of life are at risk of death from 'overwhelming cardiovascular compromise despite intensive care support'. The mechanisms of this severe disease are not completely understood. Three case histories, including that of one infant who survived, are presented. Two of the patients died despite intensive therapy with pressors and, in one child, milrinone. The third child survived following treatment with nitric oxide and sildenafil. Hence, sildenafil in combination with nitric oxide shows promise as a therapy for the haemodynamic consequences of pertussis toxaemia and this should prompt clinical trials for their efficacy for this condition.

Fatal pulmonary hypertension associated with pertussis in infants: does extracorporeal membrane oxygenation have a role?

OBJECTIVE

The deaths of 4 infants who had confirmed pertussis infection at our hospital during the past year motivated us to review their cases as well as the use of extracorporeal membrane oxygenation (ECMO) in respiratory failure caused by pertussis.

METHODS

Retrospective chart reviews of the 4 infants who had pertussis and died at Vanderbilt University Medical Center (VUMC) from May 2001 to May 2002 were conducted. The Extracorporeal Life Support Organization (ELSO) database is an international voluntary registry established in 1986 to compile passive reports of adult and pediatric patients placed on ECMO. We searched this database for pertussis cases and analyzed the clinical outcomes by age, ventilatory management, and measurements of cardiopulmonary status.

RESULTS

All 4 infants who died from pertussis infection at VUMC were younger than 3 months and had severe pulmonary hypertension, and ECMO therapy was considered for respiratory failure. Review of the international ELSO database, focusing only on children from 1986 to July 2002, revealed a total of 23,970 patients placed on ECMO. Since the first pertussis case treated with ECMO in 1990, a total of 61 children with pertussis have been treated with ECMO, representing an increase from 0.09% to 1% of the total cases. Mean age of the pertussis patients placed on ECMO was 88 days (1 day-2.7 years). The overall mortality was 70.5% (43 of 61) but was significantly higher for infants who were younger than 6 weeks (84%) compared with infants who were older than 6 weeks (61%). When evaluating pre-ECMO management, survivors had received significantly higher mean positive end expiratory pressures than nonsurvivors (11.1 +/- 4.5 vs 7.3 +/- 3.1 cmH(2)O) and had significantly higher serum pH than nonsurvivors (7.31 +/- 0.14 vs 7.14 +/- 0.19). There was no effect of duration of ECMO, positive inspiratory pressure, mean arterial pressure, ECMO mode (venoarterial vs venovenous mode), or sex on mortality.

CONCLUSIONS

Although the ECMO registry is not an active surveillance system, it suggests that the numbers of children who require ECMO for pertussis have significantly increased. The high fatality rates of pertussis patients who have placed on ECMO are alarming and should stimulate reevaluation of whether this high-risk intervention is beneficial to patients with pertussis. This review, coupled with the 4 infants who died of pertussis at VUMC, suggests that improved measures are needed to prevent pertussis in infants.

Predictors of death in infants hospitalized with pertussis: a case-control study of 16 pertussis deaths in Canada

OBJECTIVES

To describe the clinical course of fatal cases of pertussis and identify predictors of death at the time of presentation for medical care.

METHODS

Case-control study of 16 deaths from pertussis identified by the Immunization Monitoring Program, Active (IMPACT) surveillance network (January 1991-December 2001) matched with 32 nonfatal cases by age, date, and geography. Differences were compared by Fisher exact test and logistic regression. A multivariate model was developed using stepwise logistic regression.

RESULTS

All 16 fatal cases were < or =6 months old; 13 were <2 months old. Fatal cases were less likely to have had cough complications during pregnancy (48% vs 14%; P=.046) and more likely to have pneumonia (63% vs 16%; P=.0024) before hospital admission and more likely to have seizures, pneumonia, leukocytosis, and hypoxemia after admission (P<.001 for all comparisons). White blood cell count and pneumonia were independent predictors of fatal outcome in the multivariate model.

CONCLUSIONS

Infants too young to have begun their immunizations are at highest risk of fatal pertussis infection. Leukocytosis and pneumonia are predictors of a poor outcome; however, rapid progression of the disease may make interventions difficult.

[Malignant pertussis in the young infant]

Pertussis remains in France the first cause of bacterial, infectious death in infant aged 10 days to 2 months. It is especially in this age group that malignant pertussis occurs.

CASE REPORT

A 40-day-old infant was admitted in the intensive care unit with symptoms of bronchiolitis along with a 200 bpm permanent tachycardia. He presented a marked leukocytosis with lymphocytosis. On the second day, convulsions and coma occurred, followed rapidly by respiratory failure, with a subsequent deterioration due to the development of severe pulmonary hypertension. Circulatory failure caused the infant's death on the beginning of the 5th day. Pertussis was confirmed by PCR on nasopharyngeal swab. Intra-familial contamination was most likely.

COMMENTS

Malignant pertussis is characterized by the very young age of patients, permanent tachycardia sine materia, dyspnea with early respiratory failure, frequent neurological symptoms, severe hyperleukocytosis and hyperlymphocytosis, and deep hyponatremia with oliguria and edema. Mortality remains superior to 75% despite the various treatments and life support measures that have been attempted. Adult pertussis, which represents one third of the cases of prolonged cough in this age group, is the main source of contamination of non-immunized young infants. This mode of transmission stresses the importance of the generalization of pertussis vaccine booster in early adolescence, which is recommended in France since 1998. Its extension towards the adult age is under study.

Increase in deaths from pertussis among young infants in the United States in the 1990s

BACKGROUND

Severe pertussis primarily occurs among infants (<12 months of age). Despite high levels of immunization, reported pertussis cases increased in the United States in the 1990s among all age groups, including infants.

METHODS

To characterize fatal pertussis cases, we analyzed pertussis deaths reported to CDC in the 1990s and compared these with data on pertussis deaths reported in the 1980s. Data from national surveillance systems and from available medical records were used, including data from analyses of deaths reported in 1992 through 1995.

RESULTS

In 1980 through 1989, 77 pertussis deaths were reported; 61 deaths were among infants (1.67 deaths per million), including 49 among infants <4 months of age. In the 1990s 103 pertussis deaths were reported; 93 deaths were among infants (2.40 deaths per million), including 84 among infants <4 months of age. Of 89 infants with ethnicity data, 31 (36%) were Hispanic; the mortality rate among Hispanic infants (4.77 per million) was higher than among non-Hispanic infants (1.80 per million). Of 76 infants with reported gestational age, 40 (53%) were born at <37 weeks, including 22 (29%) who were born at <35 weeks. Severe pulmonary hypertension was a common lethal complication among infants.

CONCLUSIONS

Pertussis deaths increased among infants too young to be protected by immunization. A disproportionate share of deaths were complicated by pulmonary hypertension and occurred among Hispanic infants and infants born at <37 weeks gestation. New approaches to prevent infection among infants <4 months of age and improved therapies for pertussis complications are needed.

Infectious disease mortality in two Outer Hebridean islands: 1. measles, pertussis and influenza

OBJECTIVES

The purpose of the study was to examine changes in mortality from measles, pertussis (whooping cough) and influenza (all epidemic diseases) in Harris and Barra, two Outer Hebridean islands, from 1855 to 1990, and to compare the findings with those from Scotland as a whole over the same period. It was also intended to relate changes in mortality to those in social and economic factors.

MATERIALS AND METHODS

Ages and causes of death in Harris and Barra were ascertained from copies of death certificates held at the General Register Office, Edinburgh, and for Scotland as a whole from the Annual Reports of the Registrars General for Scotland. Data were standardized by calculating the Proportionate Mortality Ratio (PMR), the proportion of deaths due to a particular cause to all deaths over a given period. Spectral analysis was employed to examine the durations of epidemic cycles.

RESULTS

Ages at death increased slightly over the period of the study. For measles and pertussis, other than for the former in Harris, there were significant relationships between numbers of deaths per decade, and numbers of new susceptibles, estimated as the numbers of births. Epidemics of measles and pertussis in the islands occurred at intervals, usually separated by years of no mortality. The highest PMRs were generally during the later decades of the 19th and first decade of the 20th centuries; this may have been related to the economic problems of agriculture and fishing, and to increasing population density. Influenza epidemics were more frequent than those of the other two diseases. For all three diseases in both islands, there were significant negative power relationships between epidemic size and frequency of occurrence; those in Harris were the stronger. The relationships between length and frequency were significant only in Harris. Generally, epidemic lengths seemed less variable than sizes, possibly because of the rather 'coarse' units of length (quarters) employed. Spectral analysis of the 'detrended' data for the period before the introduction of specific immunoprophylaxis revealed that for measles the main epidemic cycle in all three populations was between 7.3 and 7.8 years' duration. Barra and Scotland had additional 2.5- and 2-year cycles, respectively. For pertussis, Harris and Barra had main cycles of 7.4 years. Harris had an additional cycle of 3.2 years. Scotland had cycles of 4 and 2 years. For influenza, Harris had a main cycle length of 7.4 years, and a less-defined one of about 2.6 years. Barra had a main cycle of 6.9 years, and a subsidiary one of 2 years. Scotland has a single cycle of 8 years. Cubic regressions of the spectral densities on cycle frequencies showed large coefficients for Harris and Barra, but small ones for Scotland. Measles coefficients were closely similar in the two islands, but not those for pertussis.

CONCLUSIONS

The findings demonstrate the episodic occurrence of epidemics of these three diseases in the two islands, as against their continual presence in the much larger population of Scotland. They reveal also the decreasing importance of these causes of death in all three populations. The data from Harris and Barra suggest that measles is a more epidemiologically 'stable' disease than pertussis. Both islands appear to obey Hamer's law of 'mass action'. The relatively long intervals between epidemics in the islands may be due partly to their isolation, and partly to the slow accumulation of sufficient numbers of susceptibles to enable an epidemic to occur.

Ecological interference between fatal diseases

An important issue in population biology is the dynamic interaction between pathogens. Interest has focused mainly on the indirect interaction of pathogen strains, mediated by cross immunity. However, a mechanism has recently been proposed for 'ecological interference' between pathogens through the removal of individuals from the susceptible pool after an acute infection. To explore this possibility, we have analysed and modelled historical measles and whooping cough records. Here we show that ecological interference is particularly strong when fatal infections permanently remove susceptibles. Disease interference has substantial dynamical consequences, making multi-annual outbreaks of different infections characteristically out of phase. So, when disease prevalence is high and is associated with significant mortality, it might be impossible to understand epidemic patterns by studying pathogens in isolation. This new ecological null model has important consequences for understanding the multi-strain dynamics of pathogens such as dengue and echoviruses.

Changes in the Dutch Bordetella pertussis population in the first 20 years after the introduction of whole-cell vaccines

Despite the introduction of mass vaccination in 1953 in The Netherlands, pertussis is currently an endemic disease with regular epidemic outbreaks. Changes in the Bordetella pertussis population in the first 20 years after the introduction of vaccination were studied by indexing IS1002 fingerprint types, fimbrial serotypes and 15 genes encoding surface proteins. Three periods were compared, the pre-vaccination period (1949-1952) and two subsequent periods, 1953-1958 and 1965-1972. Except for fimbrial serotypes, no changes were observed in the B. pertussis population between the first two periods. Mortality decreased fivefold and 543-fold in the periods 1953-1958 and 1965-1972, respectively, compared to the pre-vaccination period. The largest decrease in mortality coincided with significant changes in the B. pertussis population with respect to the frequencies of fimbrial serotypes, fingerprint types and ptxS1 alleles. A new fingerprint type (ft29), associated with the novel ptxS1 allele ptxS1A was observed in 50% of the isolates in the period 1965-1972. Of the 15 investigated genes, only ptxS1 showed a mismatch between the vaccine strains and clinical isolates, suggesting that it may have played a role in driving the observed changes. It is proposed that, within 10-20 years after the introduction of mass vaccination, an adaptive response occurred consisting of clonal expansion of strains, which expressed a pertussis toxin variant distinct from the vaccine variants. This adaptation had very little, if any, effect on mortality, however.

Epidemiology of pertussis in a West African community before and after introduction of a widespread vaccination program

The control of pertussis remains a worldwide concern. Little has been documented about its epidemiology in Africa. The authors have studied pertussis in a prospective cohort of children in a rural West African community over a 13-year period comprising time before and after introduction of a vaccination program. Children under age 15 years who were residents of the Niakhar study area in Senegal were followed prospectively between January 1984 and December 1996 for the occurrence of pertussis. Morbidity and mortality rates were extremely high before the launch of immunization. Crude incidence was 183 per 1,000 child-years at risk under age 5 years, with a 2.8% case-fatality rate. After the introduction of the vaccination program, overall incidence dropped rapidly and dramatically-by 27% after 3 years and 46% after 6 years. The decline in incidence involved all age groups but was most substantial in the group under age 5 years and was particularly pronounced in unvaccinated infants. The median age of acquisition of the disease rose steadily with population vaccine coverage. This study shows the tremendous magnitude of the disease burden in children and the rapid decline after vaccination, and it suggests a strong herd-immunity effect.

Deaths from pertussis are underestimated in England

AIMS

To improve estimates of deaths from pertussis in England and to identify reasons for under ascertainment.

METHODS

Comparison of deaths identified from enhanced laboratory pertussis surveillance, hospital episode statistics (HES), and Office for National Statistics (ONS) death registrations in England, 1994 to 1999.

RESULTS

A total of 33 deaths were identified, 88% of infants less than 4 months old. There was overlap between all sources; 22 deaths were identified in the enhanced pertussis surveillance system, 18 in ONS mortality data, and nine in HES. Children who had died from pertussis without mention of pertussis on the death certificate were more likely to have been certified by coroners than those with mention of pertussis (p = 0.0005). Using capture-recapture analysis, the total number of deaths from pertussis in the five and a half year period is estimated to be 46 (95% CI 37 to 71), or around nine deaths per year.

CONCLUSIONS

National mortality statistics significantly under estimate deaths from pertussis in England and are inadequate for monitoring the national immunisation programme. The largest number of deaths is identified through enhanced laboratory surveillance. Death registration systems should take into account available microbiological information to ensure that cause of death is accurately assigned.

Hospital admissions for pertussis in Spain, 1995-1998

This epidemiological survey was undertaken to estimate the annual burden of hospitalizations for pertussis in Spain during a four-year period 1995-1998. Data were obtained from the national surveillance system for hospital data. All hospital discharges for pertussis (ICD-9- CM 033) were analyzed. The annual incidence of hospitalization for pertussis was 1.7 per 100,000 population. Eighty-nine percent of the cases were < 1 year of age (incidence of 78 per 100,000) and 95% were < or =5 years of age (incidence of 28 per 100,000). During the study period, 14 deaths were reported among patients hospitalized by pertussis. Despite of the high immunization rates, many pertussis cases occur each year, mostly of them among very young children.

Is leukocytosis a predictor of mortality in severe pertussis infection?

Bordetella pertussis causing severe respiratory failure in infants that is unresponsive to treatment is well described. Pulmonary hypertension is a prominent feature of such cases. In this series of 13 critically ill infants with B. pertussis, hyperleukocytosis ( > 100 x 10(9)/l) was an independent predictor of death. We suggest that such extreme leukocytosis may contribute to disease severity via the formation of aggregates in the pulmonary vasculature.