Outcomes of Bordetella pertussis infection in different age groups of an immunized population

Bordetella pertussis in School-Age Children, Adolescents and Adults: A Systematic Review of Epidemiology and Mortality in Europe

Pertussis (whooping cough) epidemics persist globally despite high vaccine coverage among infants and young children. The resurgence of pertussis in high-income countries is partly due to waning vaccine immunity, resulting in a pool of unprotected adolescents and adults. However, pertussis is generally less severe in adolescents and adults, and this difference in presentation means it can often be unrecognised by healthcare professionals, meaning that it is largely under-diagnosed in older populations. A systematic search of MEDLINE, EMBASE and BIOSIS was undertaken to identify studies published between 1 January 1990 and 17 June 2019, with information on pertussis epidemiology and mortality in school-aged children, adolescents and adults in Europe. A formal statistical comparison (e.g. using meta-analyses) was not possible because of the mix of methodologies reported. There were 69 epidemiological studies and 19 mortality studies identified for review. Over the past decade, the reported incidence of notified pertussis cases varied widely between European countries, which is likely associated with differences in surveillance systems, diagnostic techniques and reporting regulations. However, several studies show that pertussis is circulating among adolescents and adults in Europe, and although pertussis-related morbidity and mortality are highest in infants, there is evidence that adults aged > 50 years are at increased risk. For example, in a hospital-based surveillance study in Portugal, between 2000 and 2015, 94% of hospitalised pertussis cases were infants aged < 1 year, with a case fatality rate (CFR) of 0.8%; however, among hospitalised adult cases of pertussis, the CFRs were 11.5% (aged 18–64 years) and 17.4% (aged > 65 years). Very few European countries currently include pertussis boosters for adults in the national immunisation strategy. In addition to increasing pertussis vaccination coverage in adolescents and adults, mitigation strategies in European countries should include improved diagnosis and treatment in these populations.

Human Immune Responses to Pertussis Vaccines

Pertussis still represents a major cause of morbidity and mortality worldwide. Although vaccination is the most powerful tool in preventing pertussis and despite nearly 70 years of universal childhood vaccination, incidence of the disease has been rising in the last two decades in countries with high vaccination coverage. Two types of vaccines are commercially available against pertussis: whole-cell pertussis vaccines (wPVs) introduced in the 1940s and still in use especially in low and middle-income countries; less reactogenic acellular pertussis vaccines (aPVs), licensed since the mid-1990s.In the last years, studies on pertussis vaccination have highlighted significant gaps and major differences between the two types of vaccines in the induction of protective anti-pertussis immunity in humans. This chapter will discuss the responses of the immune system to wPVs and aPVs, with the aim to enlighten critical points needing further efforts to reach a good level of protection in vaccinated individuals.

Pertussis without apparent cough in a disabled girl with a tracheostomy

Pertussis is characterized by intense, prolonged coughing in children often followed by a distinctive whooping sound on inspiration. However, the clinical manifestations and natural course of pertussis in disabled children are largely unknown. We experienced a case of pertussis in a disabled girl who had previously undergone a tracheostomy and laryngotracheal separation. She presented with increased tracheal secretions and required hospitalization but did not develop a cough. Pertussis was suspected from the sputum Gram stain, which revealed numerous, short gram-negative rods that did not grow on chocolate agar. A nucleic acid amplification test was positive for Bordetella pertussis and the patient improved on azithromycin. Pertussis may present without its cardinal symptoms in disabled children.

Pertussis: Microbiology, Disease, Treatment, and Prevention

Pertussis is a severe respiratory infection caused by Bordetella pertussis, and in 2008, pertussis was associated with an estimated 16 million cases and 195,000 deaths globally. Sizeable outbreaks of pertussis have been reported over the past 5 years, and disease reemergence has been the focus of international attention to develop a deeper understanding of pathogen virulence and genetic evolution of B. pertussis strains. During the past 20 years, the scientific community has recognized pertussis among adults as well as infants and children. Increased recognition that older children and adolescents are at risk for disease and may transmit B. pertussis to younger siblings has underscored the need to better understand the role of innate, humoral, and cell-mediated immunity, including the role of waning immunity. Although recognition of adult pertussis has increased in tandem with a better understanding of B. pertussis pathogenesis, pertussis in neonates and adults can manifest with atypical clinical presentations. Such disease patterns make pertussis recognition difficult and lead to delays in treatment. Ongoing research using newer tools for molecular analysis holds promise for improved understanding of pertussis epidemiology, bacterial pathogenesis, bioinformatics, and immunology. Together, these advances provide a foundation for the development of new-generation diagnostics, therapeutics, and vaccines.

Protecting Newborns Against Pertussis: Treatment and Prevention Strategies

Pertussis is a potentially severe respiratory disease, which affects all age groups from young infants to older adults and is responsible for an estimated 195,000 deaths occurred globally in 2008. Active research is ongoing to better understand the pathogenesis, immunology, and diagnosis of pertussis. For diagnosis, molecular assays (e.g., polymerase chain reaction) for detection of Bordetella pertussis have become more widely available and support improved outbreak detection. In children, pertussis vaccines have been incorporated into routine immunization schedules and deployed for pertussis outbreak control. Lower levels of vaccine coverage are now being observed in communities where vaccine hesitancy is rising. Additionally, recognition that newborn babies are at risk of pertussis in the USA and UK has led to recommendations to immunize pregnant women. Among adolescents and older adults in the USA, Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular pertussis (Tdap) Vaccines are recommended, but substantial individual- and system-level barriers exist that will make achieving national Healthy People 2020 targets for immunization challenging. Current antimicrobial regimens for pertussis are focused on reducing the severity of disease, reducing rates of sequelae, and minimizing transmission of infection to susceptible individuals. Continued surveillance for pertussis will be important to identify opportunities for reducing young infants' exposure and reducing the impact of outbreaks among school-aged children. Laboratory-based surveillance for newly emerging strains of B. pertussis will be important to identify strains that may evade protection elicited by currently available vaccines. Efforts to develop new-generation pertussis vaccines should be considered now in anticipation of vaccine development programs, which may require ten or more years to deliver a licensed vaccine.

Clinical and laboratory features of pertussis in hospitalized infants with confirmed versus probable pertussis cases

BACKGROUND

The clinical presentations of pertussis infection have considerable variation. Many infections and illnesses can cause prolonged repetitive paroxysmal cough that could be confused with Bordetella pertussis infection.

AIM

This retrospective study was designed to compare the clinico-laboratory findings between two groups of hospitalized infants with confirmed, and those who have clinical pertussis disease; to identify the possible additional diagnostic clues "for the diagnosis of confirmed pertussis disease".

SUBJECTS AND METHODS

The study population consisted of infants ≤12 months of age with clinical diagnosis of pertussis that fulfilled the World Health Organization definition for pertussis or those diagnosed by physicians. Clinico-laboratory findings were compared between two groups of patients (confirmed vs. clinical cases).

RESULTS

From a total of 118 infants admitted with a clinical diagnosis of pertussis, 16% (19/118) were confirmed by laboratory to have confirmed pertussis. Twelve of 19 (63%) and 71.99% of confirmed and clinical cases were younger than 6 months of age, respectively. For most patients, the duration of symptoms before hospitalization was <14 days. There were no significant differences between two groups of patients for paroxysmal cough and facial discoloration. However, whoop and apnea were more common among confirmed pertussis cases: P = 0.01, and P = 0.02, respectively. Leukocytosis (≥16,000/ml) (P = 0.01) and lymphocytosis (≥11,000) (P = 0.02) were reported significantly more frequently in confirmed pertussis cases.

CONCLUSION

Given the unavailability of a highly sensitive diagnostic test, in every afebrile patient with paroxysmal cough lasting for ≥7 days associated with whoop and/or apnea, particularly if accompanied by leukocytosis/lymphocytosis, pertussis disease should be considered. In this situation, prompt administration of empiric treatment for cases, and providing control measures to prevent infection transmission to contacts are recommended.

ON TWO-DIMENSIONAL WHOOPING COUGH DYNAMICS OF CONVECTION TYPE

Analyzes has been carried out for the two-dimensional whooping cough model. The solution of the arising nonlinear initial/boundary value problem is computed by a homotopy analysis method (HAM). Convergence of the derived solution is highlighted. The plotted graphs show great confidence into the used methodology of solution.

Trust and the demand for autonomy may explain the low rates of immunizations among nurses

Rates of vaccinations of healthcare workers with recommended vaccines are generally low in the developed countries. Our goals were to identify attitudes associated with self-reported vaccinations against pertussis and seasonal influenza among Israeli nurses in Mother and Child Healthcare Centers (MCHC) in the Haifa District. Over 100 nurses answered a self-administered questionnaire. Forty two percent of the nurses reported receiving the pertussis vaccine in the last five years and 44% reported receiving the influenza vaccine during the previous year. Attitudes toward the importance of vaccinating nurses, trust in the public health authorities and demand for autonomy were associated with receiving the pertussis vaccine. Attitudes toward the importance of vaccinating nurses and trust were associated with receiving the influenza vaccine in a bivariant analysis. However, in the logistic regression models only attitudes toward the importance of vaccinating nurses were associated with vaccinations [odds ratio (OR)- 3.66, 95% confidence interval (CI)- 1.4-9.6 for pertussis and OR- 4.53, CI-1.6-13.0 for influenza]. Jewish nurses reported more often receiving the influenza vaccine compared with the Arab nurses, whereas there was no difference between them in receiving the pertussis vaccine. Low levels of positive attitudes toward the importance of vaccinating nurses may inhibit nurses in MCHC from receiving vaccines. The demand for autonomy and low levels of trust may, in part, form these low levels of positive attitudes toward the importance of vaccinating nurses.

Cocooning: a concept to protect young children from infectious diseases

PURPOSE OF REVIEW

Despite focused efforts aimed at preventing infectious diseases among infants, recent years have seen a surge of infections among this population, particularly in pertussis, reminiscent of the 1940s prevaccine era. Given these trends, this review serves to discuss cocooning for infants against pertussis and its more recent application in influenza, and the barriers to and facilitators of this important strategy.

RECENT FINDINGS

Infection with pertussis and influenza remains a significant cause of hospitalization among infants aged less than 1 year. Simultaneously, uptake of both tetanus, diphtheria, and acellular pertussis (Tdap) and influenza vaccines is very low among adults reporting close contact with an infant. To date, widespread implementation of cocooning has been thwarted by both individual-level and system-level issues, although general acceptance of vaccination is high in settings in which cocooning is encouraged.

SUMMARY

Better characterization and improvement of the cocooning strategy are necessary. Additionally, longitudinal research evaluating the effectiveness of cocooning against pertussis and influenza is essential. Ultimately, the effectiveness of cocooning to produce sustained control of infections will be dependent on healthcare provider advocacy, patient education, implementation and enforcement of policies, and the development of cost-effective programs.

Pertussis serodiagnosis in Belgium from 1990 to 2009

Diagnosis of pertussis by culture and PCR is most sensitive when performed on nasopharyngeal specimens collected <2 weeks and <3 weeks, respectively, after the onset of clinical disease. Conversely, serological testing allows the diagnosis of patients (mostly adults) with less typical whooping cough symptoms, for whom clinical samples are often collected at later time points. Here, we report on a 20-year serodiagnostic survey of pertussis in Belgium from 1990 to 2009. In total, 13,163 patients were analyzed for Bordetella pertussis-specific antibodies by agglutination, complement fixation, immunofluorescence, and ELISA. The number of positive pertussis cases detected by serodiagnosis ranged between 50 and 150 annually. The mean age of positive cases increased from 9.9 years in 1990 to 33.9 years in 2009. Whereas from 1990 to 2003, children and young adolescents made up the majority of cases, from 2004 onwards, cases were detected in all age groups and the distribution became bimodal, with a first peak at the age of 10 to 20 years and a second at the age of 35 to 50 years. In contrast, patients diagnosed since 2001 by PCR and/or culture were mostly children younger than 1 year of age. Despite extensive childhood vaccination campaigns, whooping cough is still present in Belgium. Our findings confirm the potential role of adults in the continued transmission of pertussis and strongly warrant booster or cocoon vaccinations in older age groups.

Pertussis in Portugal - time for a new strategy

The introduction of routine vaccination against Bordetella pertussis led to a drastic decline in the number of reported cases of pertussis. Nevertheless, a gradual increase in pertussis notifications has been observed in the last years, and political vaccination changes have been conducted in some countries. Pertussis epidemiology is reviewed, taking into account mathematical models studies concerning new vaccinal strategies for pertussis prevention and new international recommendations. Regarding Portugal, the need for a "booster" in adolescence is emphasized, and other recommendations for pertussis control are suggested.

The seroepidemiology of Bordetella pertussis in Israel--Estimate of incidence of infection

This study was undertaken to estimate the magnitude of Bordetella pertussis infections in a highly vaccinated population in Israel in order to evaluate the relationship between clinical notification data and serology-based evidence of infection. A cross-sectional survey was conducted on a total of 1982 serum samples from the National Serum Bank, collected from January 2000 through December 2001, in order to monitor high levels of pertussis toxin (PT) IgG antibody indicative of recent B. pertussis infection, by standardized methods. The estimation yielded an infection incidence rate of 2448 per 100,000 population (> or =3 years of age) for the year 2000 compared to an annual incidence of reported pertussis of 5.6 per 100,000 for the same period. The peaks of estimated incidence of infection were found in the groups of 15-19-year olds (5245 per 100,000) and older than 60 years (6469 per 100,000), whereas the majority of clinical pertussis cases were reported for the 10-14-year olds (20.5 per 100,000). The findings clearly show that despite a high vaccination coverage rate (>93%), there is still a considerable circulation of B. pertussis, particularly in adolescents and elderly. Population-based serosurveillance for pertussis offers the potential to assist interpretation of trends independent of notification and diagnostic bias.

Bordetella pertussis isolates in Finland: serotype and fimbrial expression

BACKGROUND

Bordetella pertussis causes whooping cough or pertussis in humans. It produces several virulence factors, of which the fimbriae are considered adhesins and elicit immune responses in the host. B. pertussis has three distinct serotypes Fim2, Fim3 or Fim2,3. Generally, B. pertussis Fim2 strains predominate in unvaccinated populations, whereas Fim3 strains are often isolated in vaccinated populations. In Finland, pertussis vaccination was introduced in 1952. The whole-cell vaccine contained two strains, 18530 (Fim3) since 1962 and strain 1772 (Fim2,3) added in 1976. After that the vaccine has remained the same until 2005 when the whole-cell vaccine was replaced by the acellular vaccine containing pertussis toxin and filamentous hemagglutinin. Our aims were to study serotypes of Finnish B. pertussis isolates from 1974 to 2006 in a population with > 90% vaccination coverage and fimbrial expression of the isolates during infection. Serotyping was done by agglutination and serotype-specific antibody responses were determined by blocking ELISA.

RESULTS

Altogether, 1,109 isolates were serotyped. Before 1976, serotype distributions of Fim2, Fim3 and Fim2,3 were 67%, 19% and 10%, respectively. From 1976 to 1998, 94% of the isolates were Fim2 serotype. Since 1999, the frequency of Fim3 strains started to increase and reached 83% during a nationwide epidemic in 2003. A significant increase in level of serum IgG antibodies against purified fimbriae was observed between paired sera of 37 patients. The patients infected by Fim3 strains had antibodies which blocked the binding of monoclonal antibodies to Fim3 but not to Fim2. Moreover, about one third of the Fim2 strain infected patients developed antibodies capable of blocking of binding of both anti-Fim2 and Fim3 monoclonal antibodies.

CONCLUSION

Despite extensive vaccinations in Finland, B. pertussis Fim2 strains were the most common serotype. Emergence of Fim3 strains started in 1999 and coincided with nationwide epidemics. Results of serotype-specific antibody responses suggest that Fim2 strains could express Fim3 during infection, showing a difference in fimbrial expression between in vivo and in vitro.

Factors contributing to pertussis resurgence

Despite extensive immunization, the disease pertussis remains one of the world’s leading causes of vaccine-preventable deaths. An estimated 50 million cases and 300,000 deaths occur every year. A resurgence of pertussis is observed in highly immunized populations. Increasing numbers of pertussis are reported in adolescents and adults who transmit bacteria to newborns and infants to whom pertussis may be a life-threatening disease. Many studies have shown that the causes for the resurgence are multiple, such as increased awareness of disease, use of better diagnostic tools, improved surveillance methods and waning vaccine-induced immunity. Recently, antigenic divergence has been found between vaccine strains and clinical isolates in many countries with high vaccination coverage. Here, we summarize these findings and discuss the factors contributing to pertussis resurgence in immunized populations.

Emergency department staff and susceptibility to pertussis: a seroprevalence study

OBJECTIVE

To determine the proportion of ED staff who are susceptible to pertussis. There was evidence that some winter leave in southern Tasmania might be a reason of pertussis infection among unimmunized staff. This results in loss of individual earning and loss of availability of staff during the peak demand periods in the ED. There is evidence in the literature that underdiagnosis and undertreatment of pertussis occurs worldwide.

METHODS

All ED staff were approached to participate in this seroprevalence study. A self-completed questionnaire was used to record pervious immunization history for pertussis. Blood samples were collected and analysed to detect and quantify immunoglobulin G and immunoglobulin A titres for pertussis. All confidence intervals (CI) are at 95%.

SETTINGS

The Royal Hobart Hospital and the co-located Hobart Private Hospital.

RESULTS

Ninety-seven of 106 eligible staff took part in the present study, a participation rate of 92% (CI 84-96). Ninety-one of 97 subjects (94%, CI 87-98) believed that they had been immunized for pertussis in childhood; six subjects had either not been immunized or were unsure (6%, CI 2-13). Twenty-three subjects (24%, CI 16-33) had been immunized as adults. There was serologic evidence of recent infection for 21 participants (22%, CI 14-31). Thirty-one participants (32%, CI 23-42) were susceptible to pertussis on the basis of low immunoglobulin G titres.

CONCLUSION

ED staff should routinely be offered booster immunization for pertussis.

Booster vaccination and 1-year follow-up of 4-8-year-old children with a reduced-antigen-content dTpa-IPV vaccine

Reduced-antigen-content pertussis vaccines designed initially for booster vaccination of adolescents and adults can also be used to vaccinate pre-school age children. Combination vaccines, which reduce the number of administered injections, combine multiple antigens including inactivated poliovirus (IPV), which is recommended in this age group in some countries. This randomised, controlled study compared a combined diphtheria-tetanus-acellular pertussis-inactivated polio-containing booster vaccine, dTpa-IPV (Boostrix Polio, n=822), to separately administered dTpa (Boostrix) and IPV (IPV Mérieux, n=136) in 4-8-year-old children who had previously received four doses of DTPa. Additional serological assessment was performed 1 year after the booster dose. One month after vaccination, seroprotection/vaccine response rates were similar for both groups. At least 99.9% of the subjects had protective antibodies against diphtheria, tetanus and polio, and at least 90.1% had a vaccine response to pertussis antigens after dTpa-IPV. Reactogenicity of dTpa-IPV was comparable to dTpa + IPV. Fever and grade 3 loss of appetite occurred more commonly after dTpa-IPV, whereas swelling and grade 3 pain occurred more frequently after separately administered dTpa + IPV (P<0.05 for all). However, 95% CIs overlapped in all cases. Large swelling reactions after dTpa-IPV occurred less commonly than have been reported after a fifth dose of DTPa. One year after the booster, 98.6% of the subjects tested continued to have protective antibodies against diphtheria, tetanus and polio, and at least 81.2% were seropositive for pertussis components. The reduced-antigen-content dTpa-IPV vaccine was immunogenic, well tolerated and safe in pre-school age children. It provides immunity against four diseases in a single injection, with the potential reactogenicity benefit of a reduced-antigen dose.

Study of the risk factors for severe childhood pertussis based on hospital surveillance data

We used data collected through the French national hospital-based pertussis surveillance network to investigate the risk factors for severe childhood pertussis and more specifically the impact of the vaccination status. For infants, factors associated with a decreased risk of severe disease (defined as hospitalization in intensive care unit, assisted ventilation or death) were having received the first dose of vaccine, being seen late in the course of the disease and in a local hospital. Data also suggested that protection may increase with the number of doses administered. For older children, factors associated with a decreased risk of severity, measured by the hospitalization, were having received a recent booster injection and identification of the contaminator in the close environment. This study reinforces the need for an early start of the primary course in infants and the administration of booster injections in older children.

Immunity to pertussis 5 years after booster immunization during adolescence

BACKGROUND

We conducted a 5-year follow-up study on the persistence of pertussis-specific antibody and cell-mediated immunity after booster immunization of adolescents aged 11-13 years with a tricomponent acellular pertussis vaccine (Boostrix; trials diphtheria-tetanus-acellular pertussis [Tdap]-004/030).

METHODS

Cellular and humoral immunity to pertussis toxin (PT), filamentous hemagglutinin, and pertactin were measured in adolescents (age, 16 years) 5 years after booster immunization. Similar investigations were performed for control adolescents who had received only diphtheria and tetanus booster vaccination.

RESULTS

Five years after pertussis booster vaccination, the geometric mean concentrations of immunoglobulin G (IgG) elicited by each of the 3 pertussis vaccine antigens decreased from 1-month and 3-year postvaccination levels, but with the exception of PT IgG, were still higher than the prevaccination levels. PT IgG levels were undetectable in 28% of the subjects, but 44% of those subjects still tested positive for cell-mediated immunity to PT. Filamentous hemagglutinin IgG and pertactin IgG levels were significantly higher in Tdap-boosted adolescents than in the control subjects. Antibody concentrations at 1 month after vaccination strongly predicted antibody persistence. Cell-mediated immunity levels to PT, filamentous hemagglutinin, and pertactin persisted above the prebooster levels measured 5 years earlier.

CONCLUSIONS

The results of the present study of adolescents indicate that the interval between acellular pertussis booster immunizations might be extended beyond 5 years.

Epidemiological shift in the prevalence of pertussis in Taiwan: implications for pertussis vaccination

In Taiwan, routine pertussis immunization has been implemented for more than 40 years and a low incidence of pertussis was maintained until an 80-fold increase in cases occurred in 1992. The unexpected increase emphasized the significance of pertussis. This study evaluated a total of 2452 reported cases of pertussis during 1993–2004 and surveillance data on incidence, age distribution and seasonality. The highest morbidity was in infants aged <1 year, and upward trends in the incidence of pertussis were significant for infants aged <1 year and adolescents aged 10–14 years. The highest mean number of cases was observed in August and upward trends were in colder months. This study indicates that the epidemiology of pertussis may have been changed by waning immunity in Taiwan. Increased surveillance activities, especially in older age groups, and additional booster doses of acellular pertussis vaccine for children aged 6–8 years and adolescents/young adults aged 15–20 years are necessary to control and prevent pertussis.

Two nosocomial pertussis outbreaks and their associated costs - King County, Washington, 2004

OBJECTIVE

Pertussis outbreaks in healthcare settings result in resource-intensive control activities, but studies have rarely evaluated the associated costs. We describe and estimate costs associated with 2 nosocomial pertussis outbreaks in King County, Washington, during the period from July 25 to September 15, 2004. One outbreak occurred at a 500-bed tertiary care hospital (hospital A), and the other occurred at a 250-bed pediatric hospital (hospital B).

METHODS

We estimated the costs of each outbreak from the hospitals' perspective through standardized interviews with hospital staff and review of contact tracing logs. Direct costs included personnel time and laboratory and medication costs, whereas indirect costs were those resulting from hospital staff furloughs.

RESULTS

Hospital A incurred direct costs of $195,342 and indirect costs of $68,015; hospital B incurred direct costs of $71,130 and indirect costs of $50,000. Cost differences resulted primarily from higher personnel costs at hospital A ($134,536), compared with hospital B ($21,645). Total cost per pertussis case was $43,893 for hospital A (6 cases) and $30,282 for hospital B (4 cases). Total cost per person exposed to a pertussis patient were $357 for hospital A (738 exposures) and $164 for hospital B (737 exposures).

CONCLUSIONS

Nosocomial pertussis outbreaks result in substantial costs to hospitals, even when the number of pertussis cases is low. The cost-effectiveness of strategies to prevent nosocomial pertussis outbreaks, including vaccination of healthcare workers, should be evaluated.

Pertussis resurgence: diagnosis, treatment, prevention, and beyond

The introduction of routine vaccination against Bordetella pertussis more than a half century ago led to a drastic decline in the number of reported cases of pertussis. It was originally believed that lifelong immunity was afforded after vaccination. Unfortunately, this belief is flawed, as the highest number of pertussis cases since 1959 was reported in 2004. This significant increase has led to additional research on immunity, vaccination, and treatment of B. pertussis in all age groups. We performed a MEDLINE search of literature from 1966-2006 to evaluate and review the existing data on immunity to and prevention or treatment of B. pertussis infections. Additional articles were identified from the bibliographies of reviewed literature. Numerous articles pertaining to these topics have been published recently. The most significant changes in the management of this infectious disease surround the new recommendations by the Advisory Committee on Immunization Practices for adult and adolescent immunizations to assist in preventing outbreaks of B. pertussis. The Centers for Disease Control and Prevention recently published guidelines updating the recommended pharmacologic agents for treatment or prevention of B. pertussis. Despite decades of successful vaccination programs, pertussis continues to be a problematic disease. Fortunately, data and vaccines are now available that make development of a pertussis booster vaccination campaign reasonable. However, until widespread compliance with such programs is achieved, clinicians need to maintain vigilance against pertussis.

Pertussis in rural populations of Saskatchewan (1995 to 2003): incidence, seasonality, and differences among cases

BACKGROUND

Few Canadian studies have studied re-emergent pertussis in rural areas. This study described the epidemiology of pertussis in the rural areas of the Saskatoon Regional Health Authority in Saskatchewan, and comparisons were made to the City of Saskatoon.

METHODS

Analyses were based on passive surveillance data collected between 1995 and 2003. Estimates of the cumulative incidence (per 10,000 population) measured the occurrence of pertussis. Kaplan-Meier curves were plotted to compare a case's time until disease from their last vaccination by different vaccine types (whole-cell (WCV), or acellular (ACV)) and vaccine histories (complete or partial). Epidemic curves identified peaks in the incidence and checked for seasonal variation in case reporting.

RESULTS

Over the 9-year period, 1,135 cases were reported. Rural areas had higher incidence rates and lower proportions of cases vaccinated than urban areas. Overall, the highest age-specific incidence was observed in people aged 10-19 years. Cases aged 0-9 years vaccinated with the ACV, from both rural and urban areas, presented a shorter time to disease (14 months (95% CI: 13-16) and 17 months (95% CI: 11-21), respectively) when compared to cases vaccinated with the WCV (47 months (95% CI: 40-51) and 36 months (95% CI: 31-41), respectively), or with a combination of the two vaccines (40 months (95% CI: 27-47) and 44 months (95% CI: 36-51), respectively, p<0.01). Epidemic curves revealed that reported cases are occurring earlier in successive years (1997, 1999, and 2003) in rural areas.

CONCLUSION

Epidemiologic differences among cases from rural areas exist when compared to urban areas. This study further emphasizes the need to better understand age-, vaccine-, and seasonally-related aspects of pertussis epidemiology in rural areas.

Outbreak of pertussis in a neonatal intensive care unit--Louisiana, 2004

BACKGROUND

On November 12, 2004, a 5-month-old infant, admitted in the neonatal intensive care unit (NICU) of a Louisiana regional hospital since birth, was diagnosed with pertussis. Measures to prevent further transmission, in the NICU and beyond, were immediately put into place.

METHODS

Exposed contacts were identified among other patients of the NICU, health care workers, and family members. All were offered pertussis testing and prophylactic treatment.

RESULTS

The source of the outbreak was not identified. Despite the immediate implementation of control measures, a total of 37 additional NICU patients, 198 health care workers, and 15 family members were identified as potentially exposed contacts. Three more infants were diagnosed with pertussis, one of them after having been transferred to the NICU of another hospital in the state.

CONCLUSION

The source of this outbreak was believed to be an adult, either a hospital worker or an outside visitor. The incident clearly illustrates the infection control challenges for hospital units serving newborns and young infants in an era of changing epidemiology of pertussis.

Immunogenicity and reactogenicity of a reduced-antigen-content diphtheria-tetanus-acellular pertussis vaccine in healthy Taiwanese children and adolescents

PURPOSE

Disease caused by Bordetella pertussis is increasingly being identified among older children and adults in immunized populations, indicating a waning of the vaccine-induced immunity. These findings suggest the need for booster immunization of older children and adults. Modern acellular reduced-antigen-content vaccines have been developed, which can be given as a booster in individuals more than 4 years of age. This study was to assess the immunogenicity and reactogenicity of Boostrix, GlaxoSmithKline Biologicals' reduced-antigen-content diphtheria-tetanus acellular pertussis (dTpa) vaccine, when administered as a booster in healthy subjects previously primed with DTP vaccine.

METHODS

Healthy Taiwanese children and adolescents aged 6-8 years and 15-20 years, previously primed with DTP vaccine, were enrolled. All received one dose of Boostrix. Two blood samples were taken from each of them, one before vaccination and one at 1 month after vaccination. Serum antibodies to diphtheria and tetanus toxoids and immunoglobulin G (IgG) antibodies against the pertussis components PT, FHA and PRN were measured by enzyme-linked immunosorbent assay (ELISA) technique. Adverse reactions following vaccination were recorded.

RESULTS

A total of 180 subjects were recruited. The vaccine response rates to the pertussis antigens ranged between 89.0-100%. There were no serious adverse events reported during the study period.

CONCLUSIONS

The results of this study suggest that Boostrix may be safely and effectively administered as a booster dose to children previously primed with DTP vaccine.

Clearance of Bordetella parapertussis from the lower respiratory tract requires humoral and cellular immunity

Bordetella parapertussis and Bordetella pertussis are closely related species that cause whooping cough, an acute, immunizing disease. Their coexistence in the same host populations at the same time and vaccine studies showing that B. pertussis vaccines have little effect on B. parapertussis infection or disease suggest that the protective immunity induced by each does not efficiently cross protect against the other. Although the mechanisms of protective immunity to B. pertussis have been well studied, those of B. parapertussis have not. The present study explores the mechanism by which B. parapertussis is cleared from the lower respiratory tract by anamnestic immunity. Serum antibodies are necessary and sufficient for elimination of this bacterium, and CD4(+) T cells, complement, and neutrophils are required for serum antibody-mediated clearance. Mice lacking immunoglobulin A had no defect in their ability to control or clear infection. Interestingly, serum antibody-mediated clearance of B. parapertussis did not require Fc receptors that are required for antibody-mediated clearance of B. pertussis. Together these data support a model for the mechanism of protective immunity to B. parapertussis that is similar but distinct from that of B. pertussis.

Pertussis antitoxin decay after vaccination with DTPa

Longitudinal serum samples were collected from 542 children that had participated in a Swedish pertussis vaccine trial 1992-1995 [Gustafsson L, Hallander HO, Olin P, Reizenstein E, Storsaeter J. A controlled trial of a two-component acellular, a five-component acellular, and a whole-cell pertussis vaccine. N Engl J Med 1996;334(6):349-355] and who did not contract pertussis. The sera were analyzed for post vaccination antibody decay and for booster response of anti-PT (IgG antibodies against pertussis toxin), as measured by ELISA. Generally, an initial rapid decay of antitoxin antibody concentration was followed by a slower decay; the change occurring when the geometric mean level of antitoxin concentration reached 8-9 ELISA Units/mL (EU/mL). The time needed to reach this level was 8-9 months after the third dose in a 2, 4, and 6 months schedule. A "best-fit" combined regression model was used to predict when 50% of the children have less than the minimum level of detection of anti-PT (1EU/mL). This occurred about 65 months after dose 3 at an age of 6 years. The anti-PT response to a booster dose was evident but the post-booster geometric mean values decreased with number of years after the third dose and the response appeared later. The results indicate that a pre-school booster might be considered at 6 years of age or earlier.

Pertussis immunization in the global pertussis initiative North American region: recommended strategies and implementation considerations

In North America, children currently receive 5 doses of a combined diphtheria-tetanus-acellular pertussis vaccine between the ages of 2 months and 6 years. Although this schedule has reduced the incidence of childhood pertussis, it has not led to the development of herd immunity in the total population, largely because pertussis immunity wanes with time. The time course over which immunity wanes is uncertain; however, high pertussis antibody titers in adolescents and adults indicate unrecognized infection in these groups. There is evidence that this group serves as a source of infection for young infants who are not fully immunized. Therefore, of the potential strategies reviewed by the North American Global Pertussis Initiative group, universal adolescent immunization would in theory reduce the risk of pertussis in this age group and may reduce transmission to young infants. However, because immunity probably wanes at the same rate in adolescents and children, the burden of disease will likely shift to older age groups, including young adults (parents of vulnerable infants). Therefore the ideal would be immunization of adolescents and adults, particularly those who are in contact with young infants. Adolescent immunization is already recommended in Austria, France, Germany and Canada, and participants in the Global Pertussis Initiative recommend that this strategy be implemented across North America with a view to eventually extending immunization to include adults. The final decision to implement such a strategy will depend on pertussis surveillance studies and analysis of the effectiveness and tolerability of adolescent and adult pertussis immunization as well as program considerations related to feasibility and economics.

Potential strategies to reduce the burden of pertussis

Pertussis continues to be a significant cause of morbidity and mortality among nonimmunized young infants. Although the inception of childhood pertussis immunization programs has significantly reduced the occurrence of the disease in children, waning vaccine-induced immunity permits the disease to affect adolescents and adults, who in turn transmit the disease to unimmunized or incompletely immunized infants. The Global Pertussis Initiative brought together experts from 17 countries around the world to evaluate strategies to improve disease control. Seven strategies were considered: (1) universal adult immunization; (2) selective immunization of mothers and close family contacts of newborns; (3) selective immunization of health care workers; (4) selective immunization of child care workers; (5) universal immunization of adolescents; (6) preschool booster at 4-6 years of age; and (7) reinforcement and/or improvement of current infant and toddler immunization strategies. Because immunization programs vary widely from country to country, no single strategy is likely to be appropriate for all. Moreover it would be helpful to have additional data to support the strategies and provide a better understanding of the disease so that new approaches can be monitored effectively. However, certain steps can be taken now to reduce the incidence of pertussis.

Using computer simulations to compare pertussis vaccination strategies in Australia

High levels of notified pertussis in adolescents and adults, persisting severe disease (hospitalization and deaths) in infants despite high childhood immunization coverage, together with the availability of adult-formulated pertussis vaccines, have made alternate strategies for vaccine control of pertussis an important issue in Australia. An age-structured computer simulation model was used to compare the likely effects of adopting different vaccination strategies in Australia on pertussis transmission by age group over a 50 year time period. Epidemiological parameters and vaccination coverage in Australia were estimated from previous pertussis modeling studies and existing data. In the simulations, replacing the pertussis booster at 18 months with a booster dose for adolescents at an age between 12 and 17 years, assuming 80% coverage, led to decreases in pertussis cases of 30% in children of ages 0-23 months (who have the highest complication rates) and of 25% in adolescents, but an increase of 15% in cases in 2-4-year-old children. The simulations did not suggest any shift of pertussis cases into the adult child-bearing years. Varying parameter values in the simulations in a series of sensitivity analyses showed the model predictions to be robust over a plausible range. The results of these simulations suggest that the recent change in the Australian pertussis vaccination schedule, replacing the 18 month dose with a pertussis booster in 15-17-year-old adolescents, is very likely to reduce overall pertussis incidence in Australia without increasing the cost of the current vaccine program.

Management of acute bronchitis in healthy adults

Acute respiratory infections (ARIs) are the most common infections in humans, accounting for half of all acute conditions each year in the United States. Acute bronchitis episodes represent a significant portion of these illnesses. This article focuses on acute bronchitis in otherwise healthy individuals.

Anti-diphtheria antibody seroprotection rates are similar 10 years after vaccination with dTpa or DTPa using a mathematical model

The reduced antigen content diphtheria, tetanus and pertussis (dTpa) vaccine (Boostrixtrade mark) has been shown to induce a strong booster response to all the vaccine components in 4-6 year olds. However, anti-diphtheria antibody levels were observed to be lower when compared to the "full strength" paediatric DTPa vaccine. To assess the impact of this difference on long-term protection, a mathematical model was developed to predict diphtheria antibody decay over time. The model was based on a linear decrease in log-transformed antibody concentrations after the first year post-vaccination. When applied to data collected 3.5 years after vaccination of 4-6 year olds with either DTPa or dTpa, the model predicted that 10 years post-vaccination, 98.6% of subjects vaccinated with dTpa were likely to remain seroprotected against diphtheria, compared to 99.6% vaccinated with DTPa. Therefore, the difference observed in diphtheria antibody geometric mean concentrations 1 month after booster vaccination at 4-6 years with dTpa or DTPa is unlikely to be of clinical relevance 10 years later at the time of the adolescent booster.

Adolescent and adult pertussis vaccination: computer simulations of five new strategies

Approximately one million adult pertussis cases occur annually in the US, and infants still die from pertussis. Computer simulations were used to predict the impact of vaccination of children, adults and/or adolescents, and household members of newborns (cocoon strategy). Childhood vaccination greatly reduced cases in children, but increased the incidence in adolescents and adults. Routine adolescent and adult vaccination had a large direct effect, whereas the cocoon strategy had a predominantly indirect effect on young infants. The number needed to vaccinate (NNV) to prevent a case of typical pertussis in the entire population was lowest for the adolescent strategy. The cocoon strategy had the lowest NNV to prevent a case of typical pertussis in young infants. The current vaccination schedule, local epidemiological data, age-specific cost of pertussis cases, and accessibility of the target population will determine which strategy has the highest likelihood of success in achieving the public health goal.

Pertussis-specific cell-mediated and humoral immunity in adolescents 3 years after booster immunization with acellular pertussis vaccine

We evaluated pertussis-specific cell-mediated immunity (CMI) and humoral immunity in adolescents 3 years after they received an acellular pertussis booster immunization. Two hundred sixty-four adolescents were examined for immunoglobulin G antibodies, and 49 were examined for CMI against Bordetella pertussis antigens 40 months after receiving the booster. A control group of similarly aged adolescents who had received diphtheria and tetanus vaccination 3 years earlier was included for comparison. Pertussis-specific CMI persisted at greater than prebooster immunization levels. Although they had decreased by the 3-year follow-up, antibody levels remained significantly higher than prebooster immunization levels. Antibodies against pertussis antigens and CMI against filamentous hemagglutinin and pertactin were significantly higher in vaccinated adolescents than in control subjects. The acellular pertussis booster immunization provides long-term CMI and humoral immunity lasting for >or=3 years. The significantly higher immunity observed in the diphtheria, tetanus, and acellular pertussis vaccine recipients, compared with that in control subjects, indicates that these responses are more likely to have resulted from the booster immunization than from the boosting effects of natural B. pertussis infection.

Persistence of antibodies at 5–6 years of age for children who had received a primary series vaccination with a pentavalent whole-cell pertussis vaccine and a first booster with a pentavalent acellular pertussis vaccine: immunogenicity and tolerance of second booster with a tetravalent acellular vaccine at 5–6 years of age

The main objective of this study was to assess in 5-6-year-old French children (n=162) the persistence of antibodies induced by a primary series vaccination (at 2-4 months of age) with a pentavalent whole-cell pertussis combined vaccine (DTwcP-IPV-Hib; Pentacoq) and a first booster (at 12-16 months of age) with a pentavalent two-component acellular pertussis combined vaccine (DTacP-IPV-Hib; Pentavac). The second objective was to evaluate in these 5-6-year-old French children the safety and the immunogenicity of a tetravalent pertussis combined vaccine (DTacP-IPV, Tetravac) given as a second booster.

RESULTS

before the 2nd booster, more than 90% of children had antibody titers above the defined threshold for polyribosyl ribitol phosphate (PRP), tetanus, diphtheria and poliomyelitis; antibody titers were very low for pertussis. One month after the second booster, all children had sero-protective post-booster titers for tetanus, diphtheria and poliomyelitis types 1-3; over 90% of children had a four-fold rise in titers against DTacP-IPV antigens. Adverse events were mostly solicited reactions, with no serious adverse event. A strong anamnestic response was also observed after the second booster injection with Tetravac, with a satisfactory safety profile.

CONCLUSION

Pentavac and Tetravac (acellular pertussis containing vaccines) may thus be administered as first and second boosters respectively, in children primed with Pentacoq (whole-cell pertussis containing vaccine).

Antibody persistence against diphtheria, tetanus, pertussis, poliomyelitis and Haemophilus influenzae type b (Hib) in 5–6-year-old children after primary vaccination and first booster with a pentavalent combined acellular pertussis vaccine: immunogenicity and tolerance of a tetravalent combined acellular pertussis vaccine given as a second booster

The main objective of this study was to assess in 5-6-year-old French children (n=234) the persistence of antibodies induced by a primary series vaccination (at 2-4 months of age) and a first booster (at 12-16 months of age) with a pentavalent two-component acellular pertussis combined vaccine (DTacP-IPV-Hib; Pentavac). The second objective was to evaluate in these 5-6-year-old French children the safety and the immunogenicity of a tetravalent acellular pertussis combined vaccine (DTacP-IPV; Tetravac) given as second booster.

RESULTS

Seroprotective antibody levels against diphtheria, tetanus, types 1-3 poliomyelitis and PRP were maintained 4-5 years after primary-vaccination and first booster with Pentavac. As expected, anti-PT antibodies levels were low, suggesting that children were not colonised by Bordetella pertussis. The second booster with Tetravac was well tolerated and elicited a strong booster response for all antigens.

CONCLUSION

acellular pertussis combined vaccine, used in primary-vaccination, could be considered as having the same priming effect and the same efficacy as whole cell pertussis vaccine.

Pertussis of adults and infants

Bordetella pertussis continues to circulate even in populations where a high vaccine coverage of infants and children is achieved. Cases in adolescents and adults are reported with increasing frequency in many countries. Adults are a reservoir for infections in very young infants, in whom pertussis may be severe and life-threatening. The salient clinical feature of pertussis in adolescents and adults is prolonged coughing, and recognising that pertussis does occur in these age groups is the most important step in its diagnosis. A laboratory diagnosis can be made by bordetella-PCR from nasopharyngeal swabs or secretions and by detection of antibodies, mainly to pertussis toxin; laboratory diagnosis is, however, not well standardised. Vaccination of adolescents and adults is now possible with acellular pertussis vaccines, which are well tolerated, immunogenic, and effective. Adolescent boosters and the vaccination of health-care workers are already included in vaccination calendars in some countries. Vaccine-recommending bodies and national health-care organisations must have locally relevant information on the transmission of pertussis from adults to infants to be able to make decisions on the advisability, feasibility, and priority for booster immunisation against pertussis.

Which strategy for pertussis vaccination today?

Pertussis (whooping cough) remains an epidemic disease responsible for infant and child morbidity and mortality, and is perceived as a serious public health problem. Since the widespread use of whole-cell pertussis vaccines in the 1940s, vaccination programs have varied greatly between countries. National specificity is a function of several factors. The most important are: vaccine efficacy and tolerability;vaccine coverage and distribution; and vaccine acceptance by parents and professionals. During the 1970s, Sweden, England, Wales and Japan provided contrasting examples of the attitude of health authorities to the use of whole-cell vaccines. The increase in pertussis incidence was noted as a consequence of active opposition to this vaccine. The re-emergence of pertussis in the 1990s, in countries with high vaccination coverage and increased incidence of disease in individuals >15 years and <6 months of age, has drawn attention to the role of booster doses of pertussis vaccines and their introduction into regular vaccination programs. The use of acellular vaccines for booster doses for adolescents and adults would seem unambiguous because of their decreased reactogenicity, although the exact schedule has yet to be established. The choice between the two kinds of vaccines is more difficult for primary courses, where safety and efficacy profiles are similar, and the attitude towards acellular vaccines varies from country to country. In this case, the strategy adopted results from the national history of pertussis infection and from the quality of the available whole-cell vaccine. Two contrasting examples are the US, where acellular vaccines were licensed for the primary series in the 1990s, and the UK, where whole-cell vaccines are exclusively used for primary immunization. The changing epidemiology of pertussis, and its local diversification, would suggest that at present it is difficult to define a single worldwide strategy with only one kind of vaccine and one schedule. In order to control pertussis incidence, each country should continue to determine the best national vaccination program established in very close relation to the past and present epidemiological situation and available healthcare resources.

Infantile pertussis rediscovered in China

Immunization against pertussis was introduced in China in the 1960s. Since the 1970s, no culture-confirmed pertussis cases have been reported in the country. We report six infants with culture-confirmed pertussis, who were initially diagnosed as having other respiratory diseases at Beijing Children's Hospital, Beijing.

Real-time LightCycler PCR for detection and discrimination of Bordetella pertussis and Bordetella parapertussis

Real-time PCR assays based on the LightCycler technology were developed for individual (simplex PCR) and simultaneous (duplex PCR) detection and discrimination of Bordetella pertussis and Bordetella parapertussis in clinical samples. The assays were evaluated with 113 specimens from patients with and without symptoms of pertussis. Results were compared to those from conventional culture and TaqMan real-time PCR. The analytical sensitivity ranged from 0.1 to 10 CFU for B. pertussis and B. parapertussis, and intra- and interassay variations were less than 7%. Results were available within 2 h. With the simplex format, 21 of 100 samples from patients with clinical symptoms of pertussis were positive for B. pertussis and/or B. parapertussis. With the duplex format, 18 of 100 samples were positive. LightCycler PCR increased the diagnostic sensitivity over that of culture by 2.0-fold (duplex PCR) (P = 0.08) to 2.3-fold (simplex PCR) (P = 0.02). Our data suggest that duplex PCR in this format showed good analytical sensitivity but lost some sensitivity on clinical samples compared with the simplex format.