National study of infants hospitalized with pertussis in the acellular vaccine era

Pertussis immunisation strategies to optimise infant pertussis control: A narrative systematic review

OBJECTIVE

Countries routinely offering acellular pertussis vaccine, where long-term protection is not sustained, have the challenge of selecting an optimal schedule to minimise disease among young infants. We conducted a narrative systematic review and synthesis of information to evaluate different pertussis immunisation strategies at controlling pertussis disease, hospitalisation, deaths, and vaccine effectiveness among young infants.

METHODS

We conducted a review of the literature on studies about the primary, booster, and/or maternal vaccination series and synthesised findings narratively. Countries offering the first three doses of vaccine within six-months of life and a booster on or before the second year or life were defined as accelerated primary and booster schedules, respectively. Countries offering primary and booster doses later were defined as extended primary and booster schedules. All search results were screened, and articles reviewed and reconciled, by two authors. The Risk of Bias in Non-randomised Studies of Intervention tool was used to evaluate the risk of bias.

FINDINGS

A total of 98 studies were included in the analyses and the following recurring themes were described: timing of vaccination, vaccine coverage, waning immunity/vaccine effectiveness, direct and indirect effectiveness, switching from an accelerated to extended schedule, impact of changes in testing. The risk of bias was generally low to moderate for most studies.

CONCLUSION

Comparing schedules is challenging and there was insufficient evidence to that one schedule was superior to another. Countries must select a schedule that maintains high vaccine coverage and reduced the risk of delaying the delivery vaccines to protect infants.

Control of vaccine preventable diseases in Australian infants: reviewing a decade of experience with DTPa-HBV-IPV/Hib vaccine

The combined vaccine against diphtheria, tetanus, pertussis, hepatitis B, poliomyelitis, and Haemophilus influenzae b (DTPa-HBV-IPV/Hib, Infanrix Hexa, GSK) has been used for childhood immunization in Australia according to a two-, four-, six-month schedule since 2009. We reviewed data available in the Australian National Notifiable Diseases Surveillance System, annual vaccination coverage reports, the Database of Adverse Event Notifications, and peer-reviewed literature to assess vaccine coverage rates, incidence of all six vaccine preventable diseases, and the safety profile of DTPa-HBV-IPV/Hib vaccine in Australian infants over a period of ten years of exclusive use. Between 2009 and 2018 vaccine coverage for infants aged 12 months increased from 91.7% to 94.0% and from 84.9% to 92.6% for all and for Indigenous infants, respectively. Over the same time period, there were no reports of poliomyelitis, diphtheria or tetanus in infants <12 months of age. The incidence of hepatitis B among Australian infants <12 months of age remains 10 to 20-fold lower than the national average. Control of Haemophilus influenzae b (Hib) and pertussis disease has continued to be challenging. Timely administration of the primary series, as well as increasing coverage rates, particularly among Indigenous children, has contributed to improvements in Hib and pertussis disease control. The incorporation of additional strategies such as adjustment of the first vaccination encounter to six weeks of age, parental cocooning, and most recently maternal vaccination has further reduced the burden of pertussis, particularly during the first six months of life. The frequency of the ten most common adverse events related to the DTPa-HBV-IPV/Hib vaccine demonstrates an acceptable safety profile. Data collected over ten years of consistent, exclusive use of the DTPa-HBV-IPV/Hib vaccine in Australia highlights combination vaccination as a cornerstone in maintaining infant health.

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.

Prevalence of B. pertussis infection in children with clinically suspected pertussis

BACKGROUND

Pertussis is an important cause of hospitalization in children. Limited data on pertussis have been reported from China. The aim of this study was to characterize clinically suspected pertussis attributable to Bordetella pertussis among children and determine factors associated with longer duration of hospital stay in B. pertussis infection.

METHODS

Two hundred and seventeen consecutive children with clinically suspected pertussis were prospectively enrolled in the study between Jan 2016 through Aug 2017. Variables assessed included demographics, clinical symptoms and laboratory findings. Cox proportional hazards regression model were used to predict variables associated with longer duration of hospital stay.

RESULTS

Among the 217 patients with clinically suspected pertussis, B. pertussis was found in 106 (48.8%) patients. Of the 106 children with B. pertussis infection, 63 (59.4%) patients had coinfections with majority due to rhinovirus (HRV) (30.2%), Mycoplasma pneumoniae (29.2%) and human bocavirus (hBoV) (11.3%). Presence of coinfection [odds ratio (OR): 1.73, CI: 1.17-2.54], age ≤ 3 months (OR: 1.51, CI: 1.09 to 2.27), and WBC count ≥30 × 10⁹/L (OR: 1.66, CI: 1.07 to 2.84) were independently associated with a longer hospital stay.

CONCLUSIONS

B. pertussis infection had a high coinfection rate with the majority of coinfections due to HRV, M. pneumoniae and hBoV. Presence of coinfection, Age ≤3 months and WBC count ≥30 × 10⁹/L were associated with a longer hospital stay. Children admitted with pertussis need close monitoring when they had evidence of coinfection, Age ≤3 months, WBC count ≥30 × 10⁹/L.

The clinical characteristics and prognosis of pertussis among unvaccinated infants in the pediatric intensive care unit

Aim:

To evaluate the clinical characteristics, risk factors, and prognosis of pertussis in the pediatric intensive care unit.

Material and Methods:

Patients who were hospitalized in pediatric intensive care unit between January 2017 and January 2019 and diagnosed as having pertussis were retrospectively evaluated. Samples were taken from tracheal aspirate material in intubated patients and nasopharyngeal swabs in the other patients. Samples for Bordetella pertussis were studied using multiplex real-time polymerase chain reaction.

Results:

Eighteen patients were admitted to our pediatric intensive care unit with a diagnosis of pertussis. Ten patients were female (55.5%), and all patients were unvaccinated. The median age was 40 (range, 38–47.5) days and the median intensive care unit stay was 9 (range, 5–14) days. All patients had respiratory distress, 14 patients had cough (77.7%), four patients had fever (22.2%), and three patients had convulsions (16.6%). Seven patients were intubated. Three patients died of multiple organ failure and cardiogenic shock despite extracorporeal treatment. Respiratory syncytial virus was found in two patients and rhinovirus was found in one patient. The median leukocyte count was significantly higher in non-survivors than in survivors. Blood exchange was performed in three patients due to hyperleukocytosis. Pulmonary hypertension was the most common cardiac pathology detected in echocardiographic examinations.

Conclusion:

We found that high leukocyte count, viral co-infection, and severe pulmonary hypertension were associated with mortality and morbidity in pertussis.

Pertussis hospitalizations among term and preterm infants: clinical course and vaccine effectiveness

BACKGROUND

Pertussis causes severe disease in young unvaccinated infants, with preterms potentially at highest risk. We studied pertussis in hospitalized infants as related to gestational age (GA) and vaccination history.

METHODS

Medical record data of 0-2y old patients hospitalized for pertussis during 2005-2014 were linked to vaccination data. Multivariable logistic regression was used to study the association between GA and vaccination history on the clinical disease course. We compared vaccine effectiveness (VE) against hospitalization for pertussis between term and preterm infants (i.e., <37w GA) using the screening method as developed by Farrington.

RESULTS

Of 1187 records, medical data from 676 were retrieved. Of these, 12% concerned preterms, whereas they are 8% of Dutch birth cohorts. Median age at admission was 3 m for preterms and 2 m for terms (p < 0.001). Preterms more often had received pertussis vaccination (62% vs 44%; p = 0.01) and more often had coinfections (37% vs 21%; p = 0.01). Preterms tended more often to have complications, to require artificial respiration or to need admittance to the intensive care unit (ICU). Preterms had longer ICU stays (15d vs 9d; p = 0.004). Vaccinated preterms and terms had a lower median length of hospital stay and lower crude risks of apneas and the need for artificial respiration, additional oxygen, and ICU admittance than those not vaccinated. After adjustment for presence of coinfections and age at admittance, these differences were not significant, except the lower need of oxygen treatment in vaccinated terms. Effectiveness of the first vaccination against pertussis hospitalizations was 95% (95% CI 93-96%) and 73% (95% CI 20-91%) in terms and preterms, respectively. Effectiveness of the second dose of the primary vaccination series was comparable in both groups (86 and 99%, respectively).

CONCLUSIONS

Infants hospitalized for pertussis suffer from severe disease. Preterms were overrepresented, with higher need for intensive treatment and less VE of first vaccination. These findings stress the need for alternative prevention, in particular prenatal vaccination of mothers, to reduce pertussis in both groups.

SEVERE PERTUSSIS IN CHILDHOOD: UPDATE AND CONTROVERSY - SYSTEMATIC REVIEW

Objective:

Through a systematic review, this essay aimed at revising the concepts of severe pertussis, updating the epidemiology, pathophysiology, clinical presentation, antibiotic therapy and auxiliary therapeutic options for symptomatology and complications.

Data sources:

This review considered publications from the last 30years in the databases US National Library of Medicine (PubMed), Scientific Electronic Library Online (SciELO), Literatura Latino-americana e do Caribe em Ciências da Saúde (LILACS), Cochrane, Google Scholar, as well as protocols of the Ministry of Health and recommendations of the Centers for Disease Control and Prevention, related to childhood pertussis (whooping cough), with emphasis on its severe form. This research was based on keywords derived from the terms “pertussis”, “azithromycin”, “antitussives”, “leukocyte reduction” in Portuguese and English. Duplicate studies and those with unavailable full-text were excluded.

Data synthesis:

Among 556 records found, 54 were selected for analysis. Pertussis, as a reemerging disease, has affected all age groups, evidencing the transient immunity conferred by infection and vaccination. Severe cases occur in neonates and infants, with secondary viral and bacterial complications and malignant pertussis, a longside hyperleukocytosis, respiratory failure and shock. Macrolides continue to be the chosen antibiotics, while antitussives for coughing remain without efficacy. The prompt treatment in Intensive Care Units improved the prognostic in severe cases, and transfusion was promising among procedures for leukoreduction.

Conclusions:

Approaching severe pertussis in childhood remains a challenge for diagnostic and therapy, as the available therapeutic options are still unsatisfactory. Strategies of prevention are expected to reduce the occurrence of severe cases, while new studies should confirm the role of auxiliary therapies.

Protecting newborns from pertussis: The role of partner vaccination in the era of maternal immunization

OBJECTIVE(S)

While antenatal vaccination is the most effective strategy to reduce newborn pertussis infection and its associated morbidity and mortality, uptake has consistently been reported to be suboptimal. "Cocooning" or vaccination of the close contacts of newborns therefore remains an important strategy for protecting newborns when maternal vaccination has not occurred or with insufficient time for antibody transfer. This study assesses the uptake of pertussis vaccination by parents and close contacts of newborns providing insight into the vulnerability of newborns to pertussis upon discharge from hospital to their primary carers.

STUDY DESIGN

The study was conducted at three public and two private hospitals in Melbourne, Australia. A survey was administered to 689 women and/or their partners admitted on maternity wards of participating hospitals after delivery of a healthy newborn between August and December 2016. The main outcomes measured were reported vaccination rates and factors associated with uptake of pertussis vaccination. Kappa statistic and logistic regression were used to determine factors associated with vaccination.

RESULTS

70% of women and 66% of partners reported pertussis vaccination according to national recommendations. Significantly 22% of newborns were discharged to a household where neither parent reported vaccination. Compared to when maternal vaccination did occur, in families where it didn't there were low rates of vaccination of partners (83% vs 26%) and other carers, particularly carers usually resident overseas (76% vs 18.5%).

CONCLUSION(S)

While the majority of mothers and partners reported pertussis vaccination in accordance with recommended guidelines, concerningly nearly a quarter of newborns were discharged to a home where neither parent was vaccinated. When maternal vaccination did not occur, rates of vaccination of the other close contacts was poor. Educating women to encourage vaccination of partners and carers particularly those coming from overseas, prior to their arrival is an important consideration when maternal immunization does not occur. Cocooning remains an important approach to protect newborns of mothers vaccinated late or not vaccinated in pregnancy.

Bordetella pertussis

Pertussis is a highly infectious vaccine-preventable cough illness that continues to be a significant source of morbidity and mortality around the world. The majority of human illness is caused by Bordetella pertussis, and some is caused by Bordetella parapertussis. Bordetella is a Gram-negative, pleomorphic, aerobic coccobacillus. In the past several years, even countries with high immunization rates in early childhood have experienced rises in pertussis cases. Reasons for the resurgence of reported pertussis may include molecular changes in the organism and increased awareness and diagnostic capabilities, as well as lessened vaccine efficacy and waning immunity. The most morbidity and mortality with pertussis infection is seen in infants too young to benefit from immunization. Severe infection requiring hospitalization, including in an intensive care setting, is mostly seen in those under 3 months of age. As a result, research and public health actions have been aimed at better understanding and reducing the spread of Bordetella pertussis. Studies comparing the cost benefit of cocooning strategies versus immunization of pregnant women have been favorable towards immunizing pregnant women. This strategy is expected to prevent a larger number of pertussis cases, hospitalizations, and deaths in infants <1 year old while also being cost-effective. Studies have demonstrated that the source of infection in infants usually is a family member. Efforts to immunize children and adults, in particular pregnant women, need to remain strong.

Identifying Children at Risk of Malignant Bordetella pertussis Infection

OBJECTIVE

To identify factors associated with malignant pertussis.

DESIGN

A retrospective case notes review from January 2003 to August 2013. Area under the receiver-operator characteristic curve was used to determine how well vital sign and white cell characteristics within 48 hours of hospital presentation identified children with malignant pertussis.

SETTING

The national children's hospital in Auckland, New Zealand.

PATIENTS

One hundred fifty-two children with pertussis.

MEASUREMENTS AND MAIN RESULTS

There were 152 children with confirmed pertussis identified, including 11 children with malignant pertussis. The area under the receiver-operator characteristic curve was 0.88 (95% CI, 0.78-0.97) for maximum heart rate. The optimal cut-point was 180 beats/min, which predicted malignant pertussis with a sensitivity of 73% and a specificity of 91%. The area under the receiver-operator characteristic curve was 0.92 (95% CI, 0.81-1.0) for absolute neutrophil count, 0.85 (95% CI, 0.71-0.99) for total WBC count, 0.80 (95% CI, 0.63-0.96) for neutrophil-to-lymphocyte ratio, and 0.77 (95% CI, 0.58-0.92) for absolute lymphocyte count. All children with malignant pertussis had one or more of heart rate greater than 180 beats/min, total WBC count greater than 25 × 10/L, and neutrophil-to-lymphocyte ratio greater than 1.0 with an area under the receiver-operator characteristic curve of 0.96 (95% CI, 0.91-1.0) for a multivariate model that included these three variables.

CONCLUSIONS

Clinical predictors of malignant pertussis are identifiable within 48 hours of hospital presentation. Early recognition of children at risk of malignant pertussis may facilitate early referral to a PICU for advanced life support and selection for trials of investigational therapies.

The Burden of Pertussis Hospitalization in HIV-Exposed and HIV-Unexposed South African Infants

BACKGROUND

 There are limited data on pertussis in African children, including among human immunodeficiency virus (HIV)-exposed infants. We conducted population-based hospital surveillance to determine the incidence and clinical presentation of Bordetella pertussis-associated hospitalization in perinatal HIV-exposed and -unexposed infants.

METHODS

 Children <12 months of age hospitalized with any sign or symptom of respiratory illness (including suspected sepsis or apnea in neonates) were enrolled from 1 January 2015 to 31 December 2015. Detailed clinical and demographic information was recorded and respiratory samples were tested by polymerase chain reaction (PCR).

RESULTS

 The overall B. pertussis PCR positivity was 2.3% (42/1839), of which 86% (n = 36) occurred in infants <3 months of age. Bordetella pertussis was detected in 2.1% (n = 26/1257) of HIV-unexposed and 2.7% (n = 16/599) of HIV-exposed infants. The incidence (per 1000) of B. pertussis-associated hospitalization was 2.9 (95% confidence interval [CI], 1.8-4.5) and 1.9 (95% CI, 1.3-2.6) in HIV-exposed and HIV-unexposed infants, respectively (P = .09). The overall in-hospital case fatality ratio among the cases was 4.8% (2/42), both deaths of which occurred in HIV-exposed infants <3 months of age. Among cases, presence of cough ≥14 days (20.5%) and paroxysmal coughing spells (33.3%) at diagnosis were uncommon. Only 16 (38%) B. pertussis-associated hospitalizations fulfilled the Centers for Diseases Control and Prevention case definition of "definite" pertussis.

CONCLUSIONS

 Bordetella pertussis contributed to a modest proportion of all-cause respiratory illness hospitalization among black-African children, with a trend for higher incidence among HIV-exposed than HIV-unexposed infants. Maternal vaccination of pregnant women should be considered to reduce the burden of pertussis hospitalization in this population.

Parents as source of pertussis transmission in hospitalized young infants

PURPOSE

This study was planned to collect evidences of familial pertussis transmission to infants younger than 6 months of age. Understanding the dynamics of transmission of pertussis in families is essential to plan effective prevention strategies that could be integrated in pertussis control.

METHODS

The seroprevalence of IgG antibodies to pertussis toxin (PT-IgG) and prolonged cough symptoms were evaluated in parents of 55 infants aged <6 months hospitalized for confirmed pertussis. Parents of 33 infants with lower respiratory tract infection (LRTI) and parents of 57 healthy infants admitted as outpatients for hip ultrasound examination (HE) were enrolled as controls.

RESULTS

Parents of pertussis cases had PT-IgG levels significantly higher as compared to LRTI and HE parents. More than 40 % were compatible as transmitters of pertussis to their babies, since they had a level of PT-IgG ≥ 100 IU/ml, which is considered diagnostic for a recent pertussis episode. Based on serology, the percentage of pertussis cases that had at least one parent as source of infection was 49.1 %. When cough symptoms were taken into account, the percentage of parents putative transmitters of the infection to their infants increased to 56.4 %.

CONCLUSIONS

Parents are scarcely aware of the household transmission of pertussis to their newborns. Our study highlights the need to advise parents about the likelihood of transmission to the newborn and to be particularly aware of coughing symptoms in the household. Since infection can be asymptomatic, a serological survey of family members should also be considered.

Burden and Outcomes of Severe Pertussis Infection in Critically Ill Infants

OBJECTIVES

Despite World Health Organization endorsed immunization schedules, Bordetella pertussis continues to cause severe infections, predominantly in infants. There is a lack of data on the frequency and outcome of severe pertussis infections in infants requiring ICU admission. We aimed to describe admission rates, severity, mortality, and costs of pertussis infections in critically ill infants.

DESIGN

Binational observational multicenter study.

SETTING

Ten PICUs and 19 general ICUs in Australia and New Zealand contributing to the Australian and New Zealand Paediatric Intensive Care Registry.

PATIENTS

Infants below 1 year of age, requiring intensive care due to pertussis infection in Australia and New Zealand between 2002 and 2014.

MEASUREMENTS AND MAIN RESULTS

During the study period, 416 of 42,958 (1.0%) infants admitted to the ICU were diagnosed with pertussis. The estimated population-based ICU admission rate due to pertussis ranged from 2.1/100,000 infants to 18.6/100,000 infants. Admission rates were the highest among infants less than 60 days old (p < 0.0001). Two hundred six infants (49.5%) required mechanical ventilation, including 20 (4.8%) treated with high-frequency oscillatory ventilation, 16 (3.8%) with inhaled nitric oxide, and 7 (1.7%) with extracorporeal membrane oxygenation. Twenty of the 416 children (4.8%) died. The need for mechanical ventilation, high-frequency oscillatory ventilation, nitric oxide, and extracorporeal membrane oxygenation were significantly associated with mortality (p < 0.01). Direct severe pertussis-related hospitalization costs were in excess of USD$1,000,000 per year.

CONCLUSIONS

Pertussis continues to cause significant morbidity and mortality in infants, in particular during the first months of life. Improved strategies are required to reduce the significant healthcare costs and disease burden of this vaccine-preventable disease.

Incidence and Diagnosis of Pertussis in South African Children Hospitalized With Lower Respiratory Tract Infection

BACKGROUND

The incidence of pertussis in children in low- and middle-income countries is poorly described. This study aimed to prospectively investigate the incidence of pertussis in South African children hospitalized with lower respiratory tract infection (LRTI).

METHODS

Children hospitalized with LRTI in Cape Town, South Africa were enrolled over 1 year. Clinical data were collected. A nasopharyngeal (NP) swab and induced sputum (IS) were taken, and polymerase chain reaction specific for Bordetella pertussis (IS481+/hIS1001-) and Bordetella parapertussis (IS1001+) was performed.

RESULTS

A total of 460 children with median age 8 [interquartile range (IQR), 4-18] months were studied. B. pertussis was detected in 17 (3.7%) while total Bordetella spp. were identified on 23 (5.0 %) of 460 NP. Adding IS testing increased the identification of B. pertussis to 32 of 460 cases (7.0%; 95% confidence interval, 4.8%-9.7%); P = 0.028 and total Bordetella to 41 of 460 (8.9%; 95% confidence interval, 4-10%); P = 0.020. Shorter duration of symptoms [median 2 (IQR, 2-3) days versus 5 (IQR, 3-7) days; P = 0.0008] was associated with detection of B. pertussis on IS versus NP. B. pertussis was detected in 15.8% (n=3/19) of HIV-infected children, 10.9% (n = 10/92) of HIV exposed uninfected and 5.4% (n = 19/349) of HIV-unexposed uninfected children. Risk of B. pertussis decreased with each additional dose of diphtheria, tetanus and acellular pertussis vaccine [0 doses = 17.9%; 1 dose = 7.0%; 2 doses = 6.9%; and >3 doses = 6.2%].

CONCLUSIONS

Pertussis is common in South African children hospitalized with LRTI particularly if HIV exposed or infected but decreases sequentially with vaccination doses. Polymerase chain reaction on IS specimen provides confirmation earlier than NP while increasing overall diagnostic yield.

Epidemiology of pertussis-related paediatric intensive care unit (ICU) admissions in Australia, 1997-2013: an observational study

OBJECTIVE

To review the epidemiology of pertussis-related intensive care unit (ICU) admissions across Australia, over a 17-year period.

DESIGN

Retrospective descriptive study.

SETTING

Australian ICUs contributing data to the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry. The number of contributing ICUs increased over the study period, from 8 specialist paediatric ICUs in 1997 to 8 specialist paediatric and 13 general ICUs in 2013.

PARTICIPANTS

All paediatric (<16 years) ICU admissions, coded as pertussis-related, between 1 January 1997 and 31 December 2013.

RESULTS

A total of 373 pertussis-coded ICU admissions were identified in the ANZPIC Registry over the study period. Of these cases, 52.8% occurred during the 4 years of the recent Australian epidemic (2009-2012). ICU admissions were most likely to occur in infants aged younger than 6 weeks (41.8%, n=156) and aged 6 weeks to 4 months (42.9%, n=160). The median length of stay for pertussis-related ICU admissions was 3.6 days, with 77.5% of cases staying in ICU for <7 days. Approximately half of all admissions (54.8%) required some form of respiratory support, with 32.7% requiring invasive respiratory support. Over the study period, 23 deaths were recorded (6.2% of pertussis-related ICU admissions), of which 20 (87.0%) were infants <4 months old.

CONCLUSIONS

Pertussis-related ICU admissions occur primarily in infants too young to be fully protected from active immunisation. More needs to be done to protect these high-risk infants, such as maternal immunisation.

Maternal uptake of pertussis cocooning strategy and other pregnancy related recommended immunizations

Maternal immunization is an important strategy to prevent severe morbidity and mortality in mothers and their offspring. This study aimed to identify whether new parents were following immunization recommendations prior to pregnancy, during pregnancy, and postnatally. A cross-sectional survey was conducted by a questionnaire administered antenatally to pregnant women attending a maternity hospital with a follow-up telephone interview at 8-10 weeks post-delivery. Factors associated with uptake of pertussis vaccination within the previous 5 y or postnatally and influenza vaccination during pregnancy were explored using log binomial regression models. A total of 297 pregnant women completed the questionnaire. For influenza vaccine, 20.3% were immunized during pregnancy and 3.0% postnatally. For pertussis vaccine, 13.1% were vaccinated within 5 y prior to pregnancy and 31 women received the vaccine postnatally, 16 (51.6%) received the vaccine >4 weeks after delivery. Receiving a recommendation from a healthcare provider (HCP) was an independent predictor for receipt of both pertussis (RR 2.07, p < 0.001) and influenza vaccine (RR 2.26, p = 0.001). Non-English speaking mothers were significantly less likely to have received pertussis vaccination prior to pregnancy or postnatally (RR 0.24, p = 0.011). Multiparous pregnant women were less likely to have received an influenza vaccine during their current pregnancy (p = 0.015). Uptake of pregnancy related immunization is low and likely due to poor knowledge of availability, language barriers and lack of recommendations from HCPs. Strategies to improve maternal vaccine uptake should include education about recommended vaccines for both HCPs and parents and written information in a variety of languages.

Pertussis prevalence and its determinants among children with persistent cough in urban Uganda

BACKGROUND

We determined prevalence of pertussis infection and its associated host and environmental factors to generate information that would guide strategies for disease control.

METHODS

In a cross-sectional study, 449 children aged 3 months to 12 years with persistent cough lasting ≥14 days were enrolled and evaluated for pertussis using DNA polymerase chain reaction (PCR) and ELISA serology tests.

RESULTS

Pertussis prevalence was 67 (15% (95% Confidence Interval (CI): 12-18)) and 81 (20% (95% CI: 16-24)) by PCR and ELISA, respectively among 449 participating children. The prevalence was highest in children with >59 months of age despite high vaccination coverage of 94% in this age group. Study demographic and clinical characteristics were similar between pertussis and non-pertussis cases. Of the 449 children, 133 (30%) had a coughing household member and 316 (70%) did not. Among 133 children that had a coughing household member, sex of child, sharing bed with a coughing household member and having a coughing individual in the neighborhood were factors associated with pertussis. Children that had shared a bed with a coughing household individual had seven-fold likelihood of having pertussis compared to children that did not (odds ratio (OR) 7.16 (95% CI: 1.24-41.44)). Among the 316 children that did not have a coughing household member, age <23 months, having or contact with a coughing individual in neighborhood, a residence with one room, and having a caretaker with >40 years of age were the factors associated with pertussis. Age <23months was three times more likely to be associated with pertussis compared to age 24-59 months (OR 2.97 (95% CI: 1.07-8.28)).

CONCLUSION

Findings suggest high prevalence of pertussis among children with persistent cough at a health facility and it was marked in children >59 months of age, suggesting the possibility of waning immunity. The factors associated with pertussis varied by presence or absence of a coughing household member.

Predictors of disease severity in children hospitalized for pertussis during an epidemic

BACKGROUND

Australia recently experienced its worst pertussis epidemic since introduction of pertussis vaccine into the National Immunisation Program. This study aimed to determine factors associated with severe pertussis in hospitalized children during an epidemic using a novel pertussis severity scoring (PSS) system.

METHODS

This prospective, observational, multicenter study enrolled children hospitalized with laboratory confirmed pertussis from 8 tertiary pediatric hospitals during a 12 month period (May 2009-April 2010). Variables assessed included demographics, clinical symptoms and relevant medical and immunization history. Cases were scored using objective clinical findings with cases classified as either severe (PSS > 5) or not severe (PSS ≤ 5). Logistic regression models were used to predict variables associated with severe disease.

RESULTS

One hundred twenty hospitalized children 0-17 years of age were enrolled with a median PSS of 5 (interquartile range 3-7). Most (61.7%) were classified as not severe with 38.3% (46/120) severe. Most severe cases (54.3%) were <2 months of age. Presence of coinfection [odds ratio (OR): 4.82, CI: 1.66-14.00], <2 months old (OR: 4.76, CI: 1.48-15.32), fever >37.5°C (OR: 5.97, CI: 1.19-29.96) and history of prematurity (OR: 5.00, CI: 1.27-19.71) were independently associated with severe disease. A total of 70 cases in children ≥2 months of age, almost a third (n = 23) had not received pertussis vaccine.

CONCLUSIONS

Most severe pertussis occurred in young, unimmunized infants, although severe disease was also observed in children >12 months of age and previously vaccinated children. Children admitted with pertussis with evidence of coinfection, history of prematurity or fever on presentation need close monitoring.

Uptake of a government-funded pertussis-containing booster vaccination program for parents of new babies in Victoria, Australia

INTRODUCTION

An epidemic of Bordetella pertussis in Victoria, Australia, led to the implementation of a Government-funded vaccination program for parents of new babies. The rationale was to protect unimmunised infants from infection by vaccinating parents with a pertussis-containing vaccine. This is known as cocooning.

AIM

To estimate uptake of the vaccine among parents of new babies, two-and-a-half years after the program was implemented.

METHODS

A state-wide cross-sectional survey of parents was conducted to ascertain vaccine uptake, and to identify where and when the vaccination took place. Surveys were administered between 15 February and 14 March 2012, inclusive.

RESULTS

Of 6308 surveys distributed, 2510 completed surveys were returned (response rate 40%). Ninety-five surveys completed outside the study period were excluded, leaving 2415 available for analysis. Overall, 1937 (80%) mothers and 1385 (70%) fathers were vaccinated in relation to the birth of their most recent child. A majority of mothers were vaccinated in hospital (62%). Most fathers were vaccinated by a general practitioner (72%). The most common point at which mothers were vaccinated was before their child turned two weeks of age (65%). Fathers' vaccination time-point varied more widely: during pregnancy (25%); before their child turned two weeks of age (29%); and when their child was between two and eight weeks of age (28%).

CONCLUSION

Results of this survey indicated excellent uptake of the vaccine among both mothers and fathers under the Government-funded cocooning program. The findings are suggestive of an effective communications program designed to raise awareness of the risks of pertussis, and to promote availability of the funded vaccination program. The results may contribute to policy implementation of adult immunisation programs such as cocooning.

Retrospective Study of the Clinical Epidemiological Characteristics of Pertussis in Infants Prior to Their First Vaccination in the Russian Federation

INTRODUCTION

The coverage of pediatric pertussis vaccination in the Russian Federation is high, generally using a diphtheria, tetanus, and whole-cell pertussis vaccine in a 3-, 4.5-, and 6-month primary series and with a booster at 18 months of age. However, with no registered pertussis vaccines for adults, unvaccinated adolescents and adults can be a major source of infection of infants under 3 months of age.

METHODS

A multicenter, retrospective, clinical epidemiological analysis to characterize pertussis in infants aged up to 3 months who contracted pertussis and were hospitalized in four different cities in the Russian Federation was performed. Archived medical records and a questionnaire were used to collect the relevant epidemiological and clinical aspects for each case of pertussis over a 2-year period.

RESULTS

Infants in four different regions of the Russian Federation in the first 3 months of life, prior to their first pertussis vaccination, are at risk of pertussis infection. The severity is generally worse in neonates, and can lead to complications that can require intensive care.

CONCLUSION

Prior to vaccination, young infants in the Russian Federation remain vulnerable to severe pertussis, which may be worsened by their proximity to unvaccinated adults.

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.

Prevalence of antibody to Bordetella pertussis in neonates and prevalence of recent pertussis infection in pregnant women in Catalonia (Spain) in 2003 and 2013

BACKGROUND

Infections because of Bordetella pertussis still occur in infants and adults in European countries, despite vaccination coverage against pertussis being high.

METHODS

IgG antibody titers to pertussis toxin (anti-PT) were assessed using an enzyme-linked immunosorbent assay test (Serion ELISA classic) in 353 cord blood samples from neonates of a representative sample of pregnant women obtained in Catalonia (Spain) in 2013. Neonates with anti-PT titers ≤ 40 international units (IU)/mL were considered to be unprotected against pertussis. IgG-PT titers >100 IU/mL in umbilical cord samples were considered to be indicative of a current or recent pertussis infection (12 months) in pregnant women. The age-standardized prevalence of recent pertussis infection obtained in this study was compared with the prevalence obtained in 2003.

RESULTS

The mean anti-PT titer in neonates was 10.8 IU/mL and 89.8% of neonates were unprotected against pertussis. The prevalence of unprotected neonates as defined by cord blood anti-PT ≤ 40 IU/mL was 90%. The prevalence of recent pertussis infection in pregnant women as defined by cord blood anti-PT >100 IU/mL was 2%. The diphtheria-tetanus-pertussis vaccination coverage during childhood in pregnant women was 75%. The age-standardized prevalence of recent pertussis infection in pregnant women observed in this study (2.2%) was slightly higher than the prevalence obtained in 2003 (1.5%), with an odds ratio = 1.45 (95% confidence intervals: 0.5-3.9), although differences were not statistically significant.

CONCLUSIONS

Most neonates are unprotected against pertussis and pertussis infections are frequent in pregnant women in Catalonia. Infants and pregnant women should be the priority population groups for pertussis prevention programs in Catalonia.

Characteristics of pertussis outbreaks in Catalonia, Spain, 1997 to 2010

In Catalonia, pertussis outbreaks must be reported to the Department of Health. This study analyzed pertussis outbreaks between 1997 and 2010 in general and according to the characteristics of the index cases. The outbreak rate, hospitalization rate and incidence of associated cases and their 95%CI were calculated. Index cases were classified in two groups according to age (&lt;15 years and ≥15 years) and the vaccine type received: whole cell vaccine (DTwP) or acellular vaccine (DTaP). During the study period, 230 outbreaks were reported. The outbreak rate was 2.43 × 10(-6) persons-year, and outbreaks ranged from 2 to 32 cases, with a median duration of 18 days. There were 771 associated cases, with an incidence rate of 0.8 × 10(-5) persons-year.   After classifying outbreaks according to the age of the index case, 126 outbreaks (1.3 × 10(-6) persons-year) had an index case aged &lt;15 y and 87 (0.87 × 10(-6) person-year) had an index case aged ≥15 y (RR = 1.44, 95%CI 1.10-1.90; P = 0.007). Between 2003 and 2010, after the introduction of the acellular vaccine, the index case was vaccinated with DTwP vaccine in 25 outbreaks (0.43 × 10(-6) persons-year) and with DTaP vaccine in 32 outbreaks (0.55 × 10(-6) person-year) (RR = 0.78, 95%CI 0.46-1.31; P = 0.35). Of cases, 37.2% were correctly vaccinated, suggesting waning immunity of pertussis vaccine protection and endogenous circulation of pertussis. A greater number of outbreaks had an index case aged &lt;15 y. No changes in the disease incidence, associated cases and hospitalization rate were observed after the introduction of DTaP.

When is acute persistent cough in school-age children and adults whooping cough? A prospective case series study

BACKGROUND

Pertussis is a vaccine modified disease in most age groups and hence subtle in its presentation. Current diagnostic approaches require relatively invasive sampling.

AIM

To determine the incidence of B. pertussis infection among people aged 5-49 years identified in primary care with acute persistent cough using an oral fluid based diagnostic test.

DESIGN AND SETTING

Active surveillance of acute persistent cough of 2 weeks duration or greater was established in Auckland, New Zealand from May to October 2011. The 15 participating primary care practices provided care for a socioeconomically diverse population.

METHOD

Recent B. pertussis infection was determined by measurement of IgG antibodies to pertussis toxin (PT) in an oral fluid sample. An IgG antibody titre to PT of ≥70 arbitrary units defined recent infection. Participants reported symptoms at presentation and kept a cough diary.

RESULTS

A total of 226 participants were enrolled: 70 (31%) were children (5-16 years) and 156 (69%) were adults (17-49 years). Oral fluid samples were obtained from 225 participants. Ten per cent (23/225) had recent B. pertussis infection including a larger proportion of children than adults (17% versus 7%, P = 0.003). Neither cough duration nor any individual symptom discriminated between those with and without recent B. pertussis infection.

CONCLUSION

Pertussis is a frequent cause of acute persistent cough presenting to primary care. Clinical differentiation of pertussis from other causes of acute persistent cough is difficult. An oral fluid based diagnostic test, which is less invasive than other diagnostic approaches, has high acceptability in primary care.

A cocoon immunisation strategy against pertussis for infants: does it make sense for Ontario?

Pertussis deaths occur primarily among infants who have not been fully immunised. In Ontario, Canada, an adult booster dose was recently added to the publicly funded immunisation programme. We applied number-needed-to-treat analyses to estimate the number of adults that would need to be vaccinated (NNV) to prevent pertussis disease, hospitalisation and death among infants if a cocoon strategy were implemented. NNV=1/(P(M) X R) + 1/(P(F) X R), where P(M),P(F) (proportion of infants infected by mothers, fathers) were sourced from several studies. Rates of disease, hospitalisation or death (R) were derived from Ontario's reportable disease data and Discharge Abstract Database. After adjusting for under-reporting, the NNV to prevent one case, hospitalisation or death from pertussis was between 500-6,400, 12,000-63,000 and 1.1-12.8 million, respectively. Without adjustment, NNV increased to 5,000-60,000, 55,000-297,000 and 2.5-30.2 million, respectively. Rarer outcomes were associated with higher NNV. These analyses demonstrate the relative inefficiency of a cocoon strategy in Ontario, which has a well-established universal immunisation programme with relatively high coverage and low disease incidence. Other jurisdictions considering a cocoon programme should consider their local epidemiology.

Prospective nationwide surveillance of hospitalizations due to pertussis in children, 2006-2010

BACKGROUND

Frequency of pertussis is highly variable from country to country and it depends on multiple factors including case definitions and type of surveillance systems used. Many countries recently reported an increase of pertussis cases especially in infants and adolescents.

METHODS

From April 2006 to March 2011, 15-year-old patients hospitalized with suspected or proven pertussis were reported to the Swiss Pediatric Surveillance Unit. Patients with ≥14 days of cough plus paroxysms, whooping or post-tussive vomiting fulfilled the clinical case definition of pertussis. For laboratory confirmation, Bordetella pertussis polymerase chain reaction was offered free of charge.

RESULTS

Data were available from 159 of 173 reported cases and 130 (90% of them <12 months old) were eligible including 125 laboratory-confirmed B. pertussis infections. Rates per 100,000 population were 2.6 (<16 years) and 38.8 (<12 months), respectively. Most frequent complications were cyanosis (63%) and sleep disturbance (60%); 35 (27%) patients received intensive care and 1 patient died. Source of infection was known in 79 (61%) patients and was mainly a sibling, parent or both. Most patients were unimmunized (65%) or incompletely immunized (30%).

CONCLUSIONS

The high rate of pertussis hospitalization in young infants established in this surveillance project and the incomplete pertussis immunization status in almost all hospitalized patients require further efforts for improvement. In addition, introduction of pertussis immunizations for all adolescents (in 2013), young adults (in 2012) and pregnant women (in 2013) in Switzerland should increase indirect protection of vulnerable newborns and infants too young to be fully immunized.

The virulence factors of Bordetella pertussis: talented modulators of host immune response

Approximately 40 million whooping cough cases and between 200,000 and 400,000 pertussis-linked deaths are recorded each year. Although several types of vaccines are licensed and widely used, Bordetella pertussis continues to circulate in populations with high vaccine coverage of infants and children due to the waning of protection induced by the vaccination. B. pertussis typically expresses a wide array of virulence factors which promote bacterial adhesion and invasion by altering the local environment, including pertussis toxin, tracheal cytotoxin, adenylate cyclase toxin, filamentous hemagglutinin, and the lipooligosaccharide. The virulence factors of B. pertussis also possess immunomodulatory properties, exerted through their enzymatic and receptor-binding activities. Both pro- and anti-inflammatory effects are mediated, that can subvert host innate and adaptive immunity and favor the onset of a long-term infection. This review describes the capacities of B. pertussis virulence factors to modulate host immune responses and the mechanisms employed, which have been the subject of extensive research in the recent years, both in murine and human experimental systems. Knowledge of these mechanisms is gaining increasing importance, since it could provide in the near future the basis for the identification of therapeutic agents for modulating the immune system as well as novel molecular targets to treat pertussis.

Estimation of household transmission rates of pertussis and the effect of cocooning vaccination strategies on infant pertussis

BACKGROUND

Despite >50 years of universal vaccination, pertussis remains the most prevalent vaccine-preventable infectious disease in developed countries. Pertussis is often mild in adults, but can run a severe course in young infants.

METHODS

Data on transmission of pertussis within households were captured in a population-based, nationwide, prospective study performed in the Netherlands between February 2006 and December 2009. We estimated the transmission rates of pertussis with a clinically confirmed infection in 140 households, using stochastic epidemic models. Parameter estimates were used to gauge the effect of vaccinating household members (cocooning) to prevent the infection in young infants.

RESULTS

Overall transmission rates in the household were high. Fathers were less susceptible than other household members (estimated relative susceptibility of fathers = 0.44 [95% confidence interval (CI) = 0.27-0.72]), whereas mothers may be more infectious to their infants than are other household members (estimated relative infectiousness of mothers = 3.9 [95% CI = 0.59-14]). Targeted vaccination of mothers would approximately halve the probability of infants' infection. Vaccination of siblings is less effective in preventing transmission within the household, but may be as effective overall because siblings more often introduce an infection in the household. Vaccination of fathers is expected to be least effective.

CONCLUSIONS

Selective vaccination of persons in households with a young infant may substantially reduce the disease burden of pertussis in infants by reducing transmission within the household.

Surveillance of hospitalized and outpatient cases of pertussis in Catalonia from 2003 to 2009

Pertussis is a vaccine-preventable disease that generates a large number of cases and hospitalizations. In Catalonia, the vaccination schedule includes three doses of vaccine at 2, 4 and 6 mo and two booster doses at 18 mo and 4-6 y. In 2002, DTPw was replaced by DTPa. The aim of this study was to determine how the vaccination status affects pertussis hospitalizations. Cases were obtained from the epidemiological surveillance system of the Generalitat of Catalonia from 2003 to 2009. Hospitalization, immunization status and type of vaccine received in reported cases were analyzed. OR and 95% confidence intervals (CI) were calculated. To control the effect of age (< 6 mo and ≥ 6 mo) Mantel-Haenszel OR (ORMH) were calculated; statistical significance was established as p < 0.05. During the study period, 1538 cases were reported. Cases below vaccination age (< 2 mo) were excluded. A total of 265 cases were hospitalized: 137 (51.7%) had no vaccine administrated, 104 (39.2%) were correctly vaccinated according to age and 24 (9.1%) were poorly vaccinated. Correct vaccination protected against hospitalization (ORMH: 0.33; 95%CI: 0.23-0.47). Of hospitalized cases, 38 (14.3%) had received DTPw and 91 (34.2%) DTPa. Both vaccines were effective in avoiding hospitalization, and comparison showed no differences (ORMH: 0.73; 95%CI: 0.46-1.14). We highlight the importance of a correct follow-up immunization schedule in reducing the number of cases and hospitalizations.

Infant pertussis and household transmission in Korea

A recent resurgence of pertussis has raised public health concerns even in developed countries with high vaccination coverage. The aim of this study was to describe the clinical characteristics of infant pertussis, and to determine the relative importance of household transmission in Korea. The multicenter study was prospectively conducted from January 2009 to September 2011. We identified the demographic and clinical data from these patients and performed the diagnostic tests for pertussis in their household contacts. Twenty-one patients with confirmed pertussis were included in the analysis. All infections occurred in infants younger than 6 months of age (mean age, 2.5 months) who had not completed the primary DTaP vaccination except for one patient. Infants without immunization history had a significant higher lymphocytosis and longer duration of hospital stay compared to those with immunization. All were diagnosed with PCR (100%), however, culture tests showed the lowest sensitivity (42.9%). Presumed source of infection in household contacts was documented in 85.7%, mainly parents (52.6%). Pertussis had a major morbidity in young infants who were not fully immunized. Household members were responsible for pertussis transmission of infants in whom a source could be identified. The control of pertussis through booster vaccination with Tdap in family who is taking care of young infants is necessary in Korea.

Sources of pertussis infection in young infants: a review of key evidence informing targeting of the cocoon strategy

BACKGROUND

The relative contribution of different categories of contact in transmitting pertussis to very young infants, who experience the most severe morbidity, is the most important single factor determining the likely benefit of pertussis vaccination of their close contacts (the "cocooning" strategy).

OBJECTIVE

To identify, evaluate the quality of and summarise existing data on potential sources of infant pertussis infection in high income countries, focussing on infants under 6 months old.

DATA SOURCES

Online databases MEDLINE and EMBASE. Additional studies were identified from the reference lists of relevant articles. Study selection and analysis: Study quality was evaluated by standardised criteria, based on the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement. Pooled estimates of the proportion of pertussis cases attributable to various contact sources were calculated using data from the highest quality studies.

RESULTS

Nine studies met the inclusion criteria; seven included data on contacts of hospitalised infants less than 6 months old. Case definitions and methods of contact ascertainment were variable. Most identified sources were from the household, of which 39% (95%CI 33-45%) were mothers, 16% (95%CI 12-21%) fathers, and 5% (95%CI 2-10%) grandparents. Estimates for siblings (16-43%) and non-household contacts (4-22%) were more heterogeneous. For 32-52% of infant cases, no source was identified. Asymptomatic pertussis infection was found in 8-13% of contacts evaluated.

CONCLUSIONS

These data suggest that the greatest potential impact of pertussis vaccination of adults to prevent severe disease in young infants comes from vaccinating mothers, followed by fathers, with grandparents having a minor role. Siblings varied in importance and, given recent data regarding waning immunity in vaccinated children, need further study. Non-household sources are also well documented, highlighting the potential limitations of the cocoon strategy to prevent severe infant disease.

Pertussis vaccination in child care workers: room for improvement in coverage, policy and practice

Background

The “Staying Healthy in Child Care” Australian guidelines provide for illness and disease exclusions and encourage vaccination of staff in child care settings, however these requirements are not subject to accreditation and licensing, and their level of implementation is unknown. This study aimed to describe pertussis vaccination coverage in child care workers in a regional area of northern NSW during 2010; review current staff pertussis vaccination practices; and explore barriers to vaccination.

Methods

A cross sectional survey of all child care centre directors in the Hunter New England (HNE) area of northern NSW was conducted in 2010 using a computer assisted telephone interviewing service.

Results

Ninety-eight percent (319/325) of child care centres identified within the HNE area participated in the survey. Thirty-five percent (113/319) of centres indicated that they had policies concerning respiratory illness in staff members. Sixty-three percent (202/319) of centres indicated that they kept a record of staff vaccination, however, of the 170 centre’s who indicated they updated their records, 74% (125/170) only updated records if a staff member notified them. Of centres with records, 58% indicated that fewer than half of their staff were vaccinated.

Conclusion

Many childcare workers have not had a recent pertussis immunisation. This potentially places young children at risk at an age when they are most vulnerable to severe disease. With increasing use of child care, national accreditation and licensing requirements need to monitor the implementation of policies on child care worker vaccination. Higher levels of vaccination would assist in reducing the risk of pertussis cases and subsequent outbreaks in child care centres.

Immunizing parents and other close family contacts in the pediatric office setting

Additional strategies are needed to protect children from vaccine-preventable diseases. In particular, very young infants, as well as children who are immunocompromised, are at especially high risk for developing the serious consequences of vaccine-preventable diseases and cannot be immunized completely. There is some evidence that children who become infected with these diseases are exposed to pathogens through household contacts, particularly from parents or other close family contacts. Such infections likely are attributable to adults who are not fully protected from these diseases, either because their immunity to vaccine-preventable diseases has waned over time or because they have not received a vaccine. There are many challenges that have added to low adult immunization rates in the United States. One option to increase immunization coverage for parents and close family contacts of infants and vulnerable children is to provide alternative locations for these adults to be immunized, such as the pediatric office setting. Ideally, adults should receive immunizations in their medical homes; however, to provide greater protection to these adults and reduce the exposure of children to pathogens, immunizing parents or other adult family contacts in the pediatric office setting could increase immunization coverage for this population to protect themselves as well as children to whom they provide care.

Modelling the impact of extended vaccination strategies on the epidemiology of pertussis

The aim of this study was to investigate the optimal pertussis booster vaccination strategy for The Netherlands. A realistic age-structured deterministic model was designed. Assuming a steady-state situation and correcting for underreporting, the model was calibrated using notification data from the period 1996–2000. Several sensitivity analyses were performed to explore the impact of different assumptions for parameters surrounded by uncertainty (e.g. duration of protection after natural infection, underreporting factors, and transmission probabilities). The optimal age of an additional booster dose is in the range of 10–15 years, and implementation of this booster dose will reduce both symptomatic and asymptomatic infections, although the incidence of symptomatic infections in older age groups will increase. The impact of the different assumptions used in the model was in general limited. We conclude that over a wide range of assumptions, an additional booster dose can reduce the incidence of pertussis in the population.

Kinetics of the antibody response to tetanus-diphtheria-acellular pertussis vaccine in women of childbearing age and postpartum women

BACKGROUND

Because adolescents and adults act as a primary source of pertussis infection for infants, vaccination of mothers immediately postpartum is a potential strategy to reduce transmission (cocoon strategy). For this to be effective, high levels of antibodies must be achieved rapidly after vaccination. We sought to determine whether the antibody response to tetanus-diphtheria-acellular pertussis vaccine (Tdap) is sufficiently rapid to support the cocoon strategy.

METHODS

Two sequential studies were performed. The first was a nonrandomized, open study of a 5-pertussis-component Tdap vaccine (tetanus toxoid, diphtheria toxoid, pertussis toxoid [PT], filamentous hemagglutinin [FHA], fimbriae types 2 and 3 [FIM], and pertactin [PRN]) given to women of childbearing age; the second was a randomized, open study of Tdap or no vaccine in postpartum women. Serum levels of immunoglobin (Ig) G and IgA against pertussis antigens, serum levels of IgG against diphtheria and tetanus, and breast milk levels of IgA against pertussis antigens were measured at various times after vaccination.

RESULTS

In both studies, the antibody response was relatively rapid, with serum IgG and IgA levels beginning to increase noticeably by days 5-7 and approaching peak levels by day 14. Greater than 68% and 84.4% of IgG and IgA responders, respectively, achieved ≥ 90% of their maximum titer by day 14. The diphtheria and tetanus antibody kinetics followed a similar time course. Breast milk levels of IgA against PT, FHA, and FIM were first detectable at day 7, peaked by day 10, and then slowly decreased through day 28. Antibodies against PRN showed a similar response, although the peak occurred at day 14. There were no significant antibody responses in the control group.

CONCLUSIONS

Although the antibody response to a dose of Tdap in healthy nonpregnant women of child-bearing age and postpartum women occurs by day 14 and is suggestive of an anamnestic immune response, it may not be sufficiently rapid to protect infants in the first weeks of life.

Risk factors for complications in hospitalized young infants presenting with uncomplicated pertussis

OBJECTIVE

We sought to identify risk factors for complications in hospitalized young infants with uncomplicated pertussis.

METHODS

Retrospective cohort study of hospitalized infants 0 to 6 months of age with confirmed pertussis from 2005 to 2009. Subjects presenting without complications or need for initial intensive care admission were deemed to have uncomplicated pertussis. Complications during hospitalization were defined as apnea, pneumonia, seizures, or encephalopathy. Univariate analysis was performed by estimating odds ratios (OR) and 95% confidence intervals (CI) for the association between each variable and the occurrence of complications. Multivariable analysis was performed using logistic regression. Clinical variables included demographics, historical, laboratory, and imaging data.

RESULTS

Of 126 study subjects, 46 (36.5%) developed complications in the hospital: 43 with apnea (two required endotracheal intubation), seven with pneumonia, and three with seizures; there were no cases of encephalopathy and no deaths. Age less than 60 days (OR, 2.71; 95% CI, 1.08-6.82), cough duration less than 7 days (OR, 5.38; 95% CI, 1.79-16.18), history of color change (OR, 5.24; 95% CI, 1.14-24.07), parental intervention (OR, 10.05; 95% CI, 1.67-60.39), and need for oxygen in the emergency department (OR. 3.94; 95% CI. 1.37-11.36) were associated with development of complications. The median duration of cough at the time of complication was 9 days (range 2-30 days). Initial complete blood cell count and radiographic findings were not associated with complications.

CONCLUSIONS

Infants with uncomplicated pertussis may be at low risk for developing respiratory failure or death. Historical information may assist practitioners in determining risk for serious complications.

Factors associated with immunisation coverage and timeliness in New Zealand

BACKGROUND

Immunisation coverage in New Zealand is lower than what is necessary to prevent large epidemics of pertussis. Primary care is where most immunisation delivery occurs. General practices vary in their structure and organisation, both in a general sense and specifically with respect to immunisation delivery.

AIM

To identify the structural and organisational characteristics of general practices associated with higher immunisation coverage and more timely immunisation delivery.

DESIGN OF STUDY

A random sample of practices during 2005 and 2006.

SETTING

General practices in the Auckland and Midland regions, with over-sampling of indigenous Maori governance practices.

METHOD

Practice immunisation coverage and timeliness were measured. Primary care practice characteristics relevant to immunisation delivery by the practice were described. Associations of these practice characteristics with higher practice immunisation coverage and more timely immunisation delivery were determined.

RESULTS

A total of 124 (61%) of 205 eligible practices were recruited. A median (25th to 75th centile) of 71% (57-77%) of registered children at each practice were fully immunised, and 56% (40-64%) had no immunisation delay. In multivariate analyses, both practice immunisation coverage (P<0.001) and timeliness (P<0.001) decreased with increased social deprivation. After adjustment for socioeconomic deprivation, region, and governance, immunisation coverage and timeliness were better at practices that enrolled children at a younger age (coverage: P = 0.002; timeliness P = 0.007), used one of the four available practice management systems (coverage: P<0.001; timeliness: P = 0.006), and had no staff shortages (coverage: P = 0.027; timeliness: P = 0.021).

CONCLUSION

Practice immunisation coverage and timeliness vary widely in New Zealand. General organisational and structural aspects of general practices are key determinants of general practice immunisation delivery.

Increasing infant pertussis hospitalization and mortality in south Texas, 1996 to 2006

Pertussis admissions ranged from 0 to 7.4 per 10,000 hospitalizations from 1996 to 2003, and from 16.3 to 27.4 per 10,000 hospitalizations from 2004 to 2006. A total of 78% of patients were <4 months old, and 52% had a sick contact that was a family member. A total of 29% of patients required intensive care unit admission, and 3 died during the last 2 years of the study.

Evaluation of pertussis immunity status in schoolchildren immunized with whole-cell vaccine

It has recently been reported that the worldwide increase in the number of pertussis cases is a result of the waning of whole-cell vaccine-induced immunity. Thus, in this study, we aimed to investigate the pertussis immunity status of primary and secondary school students in a district of Ankara, Turkey. A total of 997 healthy students, aged 9–17 years, who had been immunized with four doses of whole-cell pertussis vaccine were included in the study. The subjects were divided into two age groups: 9–14 and 15–17 years. To determine the immune status, serum levels of IgG anti-pertussis toxin (aPT) antibody were tested by in-house ELISA and arbitrarily evaluated as non-immune [<10 ELISA units (EU)/ml], immune (10–100 EU/ml), and recent infection (>100 EU/ml). Serum samples of 997 students (559 females, 438 males) aged between 9 and 17 years (mean 13·02±2·25, median 13 years) were tested. Non-immune, immune and recent infection levels of aPT were found in 27·3%, 59·3% and 13·4% of individuals, respectively. The immune group did not have statistically significant differences between males and females (P=0·68). In the 9–14 and 15–17 years age groups, serum aPT antibody levels ⩾10 EU/ml were 73·1% and 72·2%, respectively, which did not represent any statistical difference (P=0·81). Students aged 15–17 years had a higher immunity rate than the 9–14 years group, and the percentage of students with recent infection in the 9–14 years group was higher than the 15–17 years group (P<0·001). The peak age of non-immunized subjects was 9 years (47·0%), and decreased to a minimum at age 12–13 years, and began to increase again from age 13–14 years. In contrast, the ratio of recent infection was least at age 9–10 years, began to increase, and reached a peak at 12 years, and then decreased. On the other hand, it was observed that household size and monthly income were not associated with the immunity status (P=0·65,P=0·37, respectively). The results of the present study show that levels of antibody against pertussis decreased in the younger age groups and, as a result, there is an increase in the number of pertussis cases. Thus, in order to decrease the incidence of pertussis and protect infants, we recommend the application of booster doses at regular intervals.