Confirmed Pertussis Cases Research Articles

Population-based active surveillance of pertussis hospitalization rates in two cities of China.

Hospitalization is most common for severe pertussis cases and those with serious complications caused by pertussis. In mainland China, the immunization program consists of primary vaccinations at 3, 4, and 5 months, followed by a booster at 18 months with DTaP. It remains uncertain whether the first dose at 3 months, rather than 6 weeks as WHO recommended, may increase disease burden, as delayed immunization may lead to lagged protection. This study aimed to determine pertussis hospitalization rates by active surveillance in China, shedding light on immunization strategies for better disease control. From June 1, 2021, to May 31, 2022, two Chinese cities underwent a population-based active surveillance. Suspected pertussis cases were confirmed as pertussis cases through PCR and culture. Pertussis hospitalization rates were calculated by dividing the number of laboratory confirmed pertussis cases by the hospitalization coverage rate of surveillance hospitals and the resident population. During the study period 2021-2022, pertussis hospitalization rate in Yiwu was 2.50/100,000 (95% CrI 2.48-2.53), while in Yongcheng, it was 7.90/100,000 (95% CrI 7.81-8.00). In both cities, infants aged < 1 year had the highest hospitalization rate (215.64/100,000: Yiwu; 217.65/100,000: Yongcheng), followed by the age group of 4-5 years (16.37/100,000: Yiwu; 65.70/100,000: Yongcheng). This study revealed significant pertussis hospitalization rates in China, particularly among infants aged < 1 year, highlighting the need of timely and early immunization. The higher hospitalization rates in the 4-5-year age group emphasize the importance of targeted preventive measures for preschool children to mitigate the impact of pertussis.

The resurgence of pertussis in Central Serbia in the period from June to December 2023

Abstract Background There was a registered increase in the number of confirmed pertussis cases in Central Serbia between June and December 2023. Among the possible causes of pertussis resurgence are increased awareness of pertussis among healthcare workers, availability of the sensitive RT PCR method in diagnostic, the limited duration of vaccine-induced immunity as well as decline of immunization coverage influenced by the COVID-19 pandemic. Methods The nasopharyngeal samples from clinics and primary care departments were transferred to Institute of Public Health of Serbia. DNA was extracted from each sample using the MagMAX Viral/Pathogen kit. The presence of B. pertussis was determined using two PCR assays, VIASURE Bordetella Real Time PCR Detection Kit and Bosphore B. pertussis/parapertussis Genotyping Kit, Anatolia Geneworks. Results RT-PCR confirmed a total of 338 pertussis cases in Institute of Public Health of Serbia during the observed period. Most of confirmed cases were among children 9-14 years old (49,7%) followed by infants younger than 12 months (21,9%). The more severe cases were among the unvaccinated and uncomplete vaccinated infants, 78,4% of which required hospitalization with two deaths in this age group. Conclusions Based on the analysis of the obtained results, we can highlight the importance of using sensitive methods in pathogen detection. Rapid diagnosis, laboratory confirmation and notification ensure early public health intervention to minimize the spread of disease. Despite long tradition of mandatory immunization against pertussis in the Republic of Serbia, wanning of vaccine induced immunity poses potential risk for the resurgence of pertussis. For pertussis control, in the future, it will be essential to achieve high immunization coverage as well as to introduce a booster dose of pertussis containing vaccine for children aged 14 and to implement vaccination of pregnant women. Key messages • For the better pertussis control vaccination of adolescents and adults, as well as vaccination of pregnant women should be considered in the future vaccination policies. • Clinicians should consider pertussis in the differential diagnosis of persistent cough illness in people of all ages, even those previously immunized.

Pertussis vaccine effectiveness following country-wide implementation of a hexavalent acellular pertussis immunization schedule in infants and children in Panama

ABSTRACT Despite high pediatric vaccination coverage rates (VCRs), pertussis incidence has increased worldwide, including in several countries in Latin America in the last two decades. Given the few vaccine effectiveness (VE) studies in Latin American countries, this retrospective, observational, cohort study estimated the effectiveness of hexavalent acellular (aP) primary and booster vaccination (wP) against pertussis in infants (6.5–18.5 months) and children (18.5–48.5 and 48.5–72.5 months) in Panama. Age-specific incidence rates (IRs) were calculated for the vaccine’s pre-initiation (2001–2013), initiation (2014), and post-initiation (2015–2019) periods. VCRs and trends were determined, and VE was analyzed using a case coverage or screening method to compare proportions of vaccinated cases and vaccinated individuals in the population. Between 2001–2019, 868 confirmed pertussis cases were reported in Panama; 712 (82.0%; 54.8 cases/year) during the pre-initiation period, 19 (2.2%; 19 cases/year) during the initiation period, and 137 (15.8%; 27.4 cases/year) during the post-initiation period. Panama underwent cyclical increases in IRs, which varied between age groups. VCRs increased for primary and booster doses. Between 2015 and 2019, third-dose yearly vaccine coverage increased, on average, 3.3%. Specifically, during the post-initiation period, 109/137 (79.6%) of cases were unvaccinated. Relative VE was estimated at 96.2% [95% CI: 86.5%, 98.9%] with three doses; 100% with 4 and 5 booster doses. Absolute VE was estimated at 99.3% with three doses only. These results show that vaccination played an important role in maintaining a low number of pertussis cases in Panama, affirming the need for sustained investment and commitment to vaccination programs.

Evaluation of the Completeness and Timeliness of the Infant Pertussis Surveillance System in the Czech Republic in 2015, 2017 and 2019.

The completeness and timeliness of the pertussis questionnaire-based enhanced surveillance system (ESS) among infants and reported pertussis data within the electronic nationwide notification system (NNS) in the years 2015, 2017 and 2019 were evaluated in a pilot study. The completeness of the variables for demographic characteristics, date of symptom onset, hospitalisation and vaccination status were assessed in both systems. Timeliness of reporting in the NNS was analysed as the interval between symptom onset and a) the date of first specimen collection (diagnostic delay), and b) the date of the Regional Public Health Authority receiving notification (notification delay). A total of 121 confirmed pertussis cases were reported to the NNS in the study years, while in the ESS a total of 104 confirmed cases were reported in infants. In both systems most cases were in the age group of one completed month of life (20% versus 23%) and males (55% versus 55%). The majority of cases were hospitalised (81% versus 85%) and unvaccinated (77% versus 78%). Within the NNS, the first dose of vaccine was reported in 13 cases, the second dose in 11, and third dose in three cases. Within the NNS, 100% completeness of following variables was found: symptom onset, week and region of reporting, age, gender and place of isolation. Median diagnostic delay was nine days. Median notification delay was 18 days. Data completeness was high in the NNS, except for lack of vaccination data in those eligible by age. Efforts to improve the completeness of laboratory-related variables and timeliness are essential. Based on the study results, the project of improving the ESS for infants will continue with regular evaluation.

Burden of pertussis among young infants in Malaysia: A hospital-based surveillance study

BackgroundThe case fatality rate and the risk of complications due to pertussis is very high in infants. Asia has the second highest childhood pertussis burden. The study aimed to assess the prevalence, clinical complications, and mortality rates of pertussis disease requiring hospitalization among young infants in Malaysia. MethodsThe study was a one-year, hospital-based, multi-site surveillance of infants less than six months of age with symptoms consistent with pertussis and a cross-sectional analysis of their mothers for recent pertussis infection. Information was obtained from medical records and interviews with the parents. Pertussis diagnosis was confirmed for all infants through serum anti-PT titration test or PCR test. Results441 possible cases of pertussis were included in this study. Of these, 12.7 % had laboratory confirmation of pertussis. Infants with confirmed pertussis had significantly higher rates of cyanosis (37.5 % vs 8.6 %; p < 0.0001) and apnea (12.5 % vs 3.9 %; p = 0.027) than test-negative infants. Most infants from both groups were in recovery/recovered at discharge. Those with confirmed pertussis had higher case fatality rate than test-negative cases (5.4 % vs 1.0 %; p = 0.094), but the difference did not reach significance. The majority of confirmed pertussis cases (89.3 %) occurred in infants too young to be fully vaccinated or under-vaccinated for their age. Both test-negative and confirmed pertussis resulted in work-day losses and incurred costs for both parents. ConclusionsA high pertussis disease burden persists in infants less than six months of age, especially among those un- and under-vaccinated. Maternal and complete, on-time infant vaccination is important to reduce disease burden.

Effect of change in vaccine schedule on pertussis epidemiology in France: a modelling and serological study

In April-May, 2013, France modified its pertussis vaccination schedule, which uses the acellular pertussis vaccine, from three primary doses at 2, 3, and 4 months of age and a first booster at 16-18 months of age (former schedule) to two primary doses at 2 and 4 months of age and a first booster at 11 months of age (new schedule). We aimed to assess the subsequent effect of the vaccine schedule change on pertussis epidemiology in France. In this modelling study, using data collected between Jan 1, 2012, and Dec 31, 2019, from French national surveillance sources, we analysed the PCR test results of nasopharyngeal swabs collected from symptomatic outpatients aged 2-20 years with suspected pertussis. We developed a negative binomial regression model for the number of confirmed pertussis cases by year and age to assess the relative risks of pertussis depending on vaccine schedule. The linear predictor included the year, the age group, the population size, and a proxy of waning immunity. We tested different models in which waning immunity could vary with vaccine schedule and type of primary vaccine. The models were fitted to the 2012-18 data via Bayesian Markov chain Monte Carlo sampling, and the 2019 data were left out for external model validation. We also compared the anti-pertussis toxin (PT) antibody concentrations in leftover sera from children not tested for pertussis or recent respiratory tract infection aged 2-5 years born before and after the vaccine schedule change. We collected data on 7493 confirmed cases of pertussis. The model that best fitted the 2012-18 epidemiological data supported a faster waning of immunity following vaccination with the new vaccine schedule. 3 years after vaccination, the risk of developing pertussis was 1·7 (95% CI 1·4-2·0) times higher for children vaccinated according to the new schedule than those vaccinated according to the former schedule. The model correctly predicted the age distribution of cases in 2019. Geometric mean concentrations (GMC) of anti-PT IgG were 50% lower in children aged 2 years vaccinated with the new schedule (GMC=5·85 IU/mL [95% CI 4·08-8·39]) than in children of the same age vaccinated with the former schedule (GMC=11·62 IU/mL [95% CI 9·05-14·92]; p=0·0016), and 43% lower in children aged 3 years vaccinated with the new schedule (GMC=3·88 IU/mL [95% CI 2·82-5·34]) than those with the former schedule (GMC=6·80 IU/mL [95% CI 4·77-9·70]; p=0·026). A shorter-lived protection induced by the new vaccine schedule recommended in France since 2013 is associated with an increase of pertussis cases in children aged 2-5 years. If similar findings are observed in other countries and clinical trials, these findings should be considered in future pertussis vaccination policies. INCEPTION, Labex-IBEID, Institut Pasteur, and Santé Publique France.

Risk factors for pertussis among children hospitalized for pertussis during 2016–2017, in Guizhou Province of China: a case-control study

AimPertussis is a respiratory tract infection, the vaccine for which was introduced in the Expanded Programme on Immunization (EPI) in Guizhou Province of China (hereafter referred as Guizhou) in the 1980s. This vaccine rapidly decreased incidence rates of pertussis in the province, however, despite the wide high coverage of the diphtheria, tetanus and acellular pertussis (DTaP) combined vaccine, there has been a resurgence of pertussis since 2014. Even with this recent increase in disease transmission, risk factors for pertussis infection have not been evaluated in Guizhou. We aimed to provide information on pertussis risk factors and insight on designing targeted pertussis control policies and measures through this study. MethodsA 1∶2 matched retrospective case-control study was conducted between 2016 and 2017, involving infants and children younger than 6 years old and parents of the participants. The enrolled cases included clinical and laboratory confirmed pertussis cases according to the WHO-recommended pertussis definition. Controls were selected from children in the same neighborhood who were not diagnosed with pertussis prior to our investigation and did not exhibit any clinical manifestations of pertussis. ResultsThe household size [Matched odds ratio (ORm) = 1.4, 95% confidence interval (CI): 1.1–1.7] and household members with antecedent cough (ORm = 3.6, 95% CI: 1.8–7.2) were significantly associated with their child’s pertussis onset. The parents’ occupations were significantly associated with their child’s pertussis onset (ORm = 9.4, 95% CI: 1.6–54.8, for mother side; ORm = 4.5, 95% CI: 1.2–16.5, for father side), when they worked in the business and/or service industry. Having family members with a history of cough was an independent risk factor for pertussis [Adjusted odds ratio (AOR) = 43.6, 95% CI: 2.7–694.0]. Besides, the parents' demographic characteristics and DTaP doses were not found to be independent factors. ConclusionHousehold exposure is an important risk factor for pertussis infection in infants and young children and should therefore be considered as a major factor during formulation of pertussis control policies and measures.

Pertussis outbreak in southern Ethiopia: challenges of detection, management, and response

BackgroundDespite the availability of effective vaccines, pertussis remains endemic with high fatality rates in low and middle-income countries (LMIC). This study aims to describe an outbreak of pertussis in a health district of Ethiopia. The study highlights the challenges faced by the health system in identifying pertussis cases and appropriately responding to the outbreak at the district level.MethodsA descriptive cross-sectional study was conducted using data sourced from the District Public Health Emergency and Management (PHEM) surveillance service and outbreak management field reports. Stratified attack rates and fatality rates for pertussis are described. Systemic problems leading to the outbreak are explored and narrated. A modified CDC pertussis case definition was employed with a polymerase chain reaction used to confirm cases.ResultsFrom September 2018 to January 2019, 1840 suspected, probable, and confirmed pertussis cases and six deaths were identified. Pertussis cases ranged from 1 month to 51 years in age. An outbreak occurred in 14 out of the 24 villages of Dara Malo district. The overall attack rate was 1708 per 100,000 population with a fatality rate of 3.3 per 1000 pertussis cases. The highest attack rate of 12,689/100,000 was seen in infants. Among confirmed, probable and suspected pertussis cases, only 41.1% had completed the three-dose pertussis vaccine’s primary schedule. The household survey revealed a population coverage of 73.4 and 40.8% for Pentavalent vaccine dose one and three respectively. Investigations suggested the existence of a poor cold chain management system in the study area.ConclusionsThere is an urgent need to build capacity to strengthen routine vaccination services and improve the maintenance of the vaccine cold chain. Other LMICs are urged to take lessons learned from this outbreak to strengthen their own vaccination programs and capacitate health workers to manage local outbreaks.

2636. Distinguishing Pertussis from Viral Mimickers: Development and Validation of a Clinical Prediction Score

BackgroundPertussis is often confused with respiratory viral infections, leading to misdiagnosis and overuse of antibiotics. Distinguishing the two entities more accurately can help optimize care.MethodsWe reviewed the charts of children under 18 years of age who presented to Sultan Qaboos University Hospital in Muscat, Oman and were tested for Bordetella pertussis by PCR between 2013 and 2018 (discovery cohort). Clinical and laboratory data were collected from the electronic patient record and analyzed. Backward conditional logistic regression was used to identify independent predictors of laboratory-confirmed pertussis cases. The Muscat Pertussis Index (MPI) score was developed based on the logistic regression model. The MPI score was retrospectively validated on a separate cohort of pediatric patients who presented to the Royal Hospital- Oman’s largest pediatric center- between 2017 and 2018, and were similarly tested for pertussis (validation cohort). Ethical approval of the study was obtained formally for both sites.Results354 patients were enrolled in the discovery cohort. 196 (55%) were male, and the median age was 10 weeks (IQR, 6–16). 57 (16%) patients tested positive for B. pertussis by PCR, while 266 (75%) tested positive for respiratory viruses. 32 (9%) patients had both pertussis and a viral co-infection and 63 (18%) were negative for both. 255 (72%) patients received macrolide antibiotics. Younger age, fewer vaccine doses, contact with a sick adult, longer symptom duration, paroxysmal cough, cyanosis, post-tussive emesis, apnea, lymphocytosis and thrombocytosis were significantly associated with pertussis (Table 1). After logistic regression, independent predictors of pertussis were longer symptom duration, lymphocytosis, paroxysmal cough, lack of fever, cyanosis and age under 8 weeks. This formed the basis for creating the MPI score (Table 2). The MPI score was validated on a cohort of 122 patients. Higher MPI scores correlated significantly with confirmed pertussis cases (area under the receiver operating characteristics curve = 0.899, P < 0.001, Figure 1 and Table 3).ConclusionThe majority of suspected pertussis cases were actually due to viral mimickers. The MPI score can predict likely cases of pertussis before laboratory confirmation. Future validation in more diverse settings would help expand its applicability. Disclosures All authors: No reported disclosures.

Challenges to Pertussis Control.

* Abbreviations: DTaP — : diphtheria-tetanus-acellular pertussis DTwP — : diphtheria, tetanus toxoids, and whole-cell pertussis KPNC — : Kaiser Permanente Northern California In this issue of Pediatrics , the vaccine research group at Kaiser Permanente Northern California (KPNC) contributed another important article outlining the challenges of pertussis control in a highly vaccinated population.1 Nearly one-half million children born between 1999 and 2016 and managed at KPNC from 2006 to 2017 were evaluated. Of those immunized children, all had received only diphtheria-tetanus-acellular pertussis (DTaP) vaccine. In total, 738 polymerase chain reaction–confirmed pertussis cases were diagnosed. Pertussis risk was 13 times higher among unvaccinated and nearly 2 times higher among undervaccinated children when compared with those who were fully vaccinated. However, >80% of the total pertussis cases were seen in children who had received all their recommended DTaP vaccine doses. Pertussis risk increased with increasing time since vaccination, clearly demonstrating waning immunity, which the KPNC group and others had previously reported.2,3 Those individuals who began their medical career after 1997, when DTaP totally replaced the conventional diphtheria, tetanus toxoids, and whole-cell pertussis (DTwP) vaccines, may question why DTaP replaced DTwP in the first place. When I began my academic career at Vanderbilt University School of Medicine in 1980, pertussis disease appeared to be well controlled.4 Rarely would cases present to the medical center, and generally … Address correspondence to Kathryn M. Edwards, MD, Division of Infectious Diseases, Department of Pediatrics, Vanderbilt University School of Medicine, 1161 21st Ave South, D-7227 Medical Center North, Nashville, TN 37232. E-mail: kathryn.edwards{at}vumc.org

Resurgence of pertussis in Taiwan during 2009-2015 and its impact on infants.

Pertussis incidence markedly decreased due to universal vaccination, but outbreaks had been noted worldwide in recent decade. This study was conducted to know the epidemiology of pertussis and its impact on infants in Taiwan. Epidemiologic parameters for confirmed pertussis cases were collected from the Taiwan Centers for Disease Control. The incidence of each age group over years was calculated using population data. We also did retrospective reviews of laboratory-confirmed pertussis cases in NTUH to analyze clinical characteristics and disease severity. A total of 668 confirmed pertussis cases were obtained from the Taiwan CDC open database between 2003 and 2017. There was higher incidence during the period 2009-2015, with a mean incidence of 0.27 cases per 100,000 population, about 2-fold increase compared with mean incidence of 0.12 cases per 100,000 population during the period 2003-2008. Infants accounted for the highest proportion of all cases (49.8%), with mean incidence of 16.1 cases per 100,000 people per year during 2009-2015, and a trend of increase was found from 2003 to 2015. In NTUH, a total of 17 laboratory-confirmed pertussis cases were diagnosed during 2012-2016, and 14 cases were young infants. Among them, 9 infants had been admitted to intensive care unit and 2 infant needed invasive ventilator support. There was a resurgence of pertussis during 2009-2015 and it had significant impact on infants. Young infants with pertussis may be severe and need intensive care, so preventive strategy may be advocated for them.

Risk factors for pertussis among hospitalized children in a high HIV prevalence setting, South Africa

BackgroundIn low- and middle-income countries, including South Africa, the epidemiology of pertussis in relation to immunization, nutritional, and HIV status is poorly described. This article reports on risk factors in South African children hospitalized with pertussis. MethodsA prospective, hospital-based, sentinel surveillance programme for pertussis was conducted in Gauteng Province, South Africa. Hospitalized children (≤10 years) meeting the surveillance criteria for clinically suspected pertussis were screened and enrolled. Nasopharyngeal specimens were collected for real-time multiplex PCR and culture of Bordetella species. ResultsBordetella pertussis was detected in 6.2% (61/992) of children. Pertussis was significantly more prevalent in infants younger than 3 months (9.8%; 38/392) and in young children between the ages of 5 and 9 years (12%; 4/34) (p=0.0013). Of the 61 confirmed pertussis cases, 17 were too young for vaccination. Of the remaining 44 infants, vaccination DTP1 was administered in 73% (32/44) of pertussis-confirmed patients who were eligible, DTP2 in 50% (16/32), DTP3 in 54% (14/26), and DTP4 in 56% (5/9) of vaccine-eligible cases at 18 months of age. B. pertussis infection was less likely in children immunized at least once (5%, 32/692) than in unvaccinated children (10%, 24/230) (p=0.0001). HIV exposure and infection status were determined in 978 (99%) patients: 69% (678/978) were HIV-unexposed and uninfected and 31% (300/978) were HIV-exposed. Of these HIV-exposed patients, 218 (22%) were proven HIV-exposed and uninfected and 82 patients were HIV-infected (8.4%, 82/978). HIV prevalence was similar in pertussis-positive (6%, 5/82) and pertussis-negative (6%, 55/896) children (p=0.90). B. pertussis infection was unrelated to poor nutritional status. ConclusionsIn South Africa, B. pertussis poses a greater risk to infants who are too young for the first vaccine dose, those who are not vaccinated in a timely manner, and those who do not receive all three primary doses. HIV infection and HIV exposure were not associated with pertussis infection.

Contact tracing with a real-time location system: A case study of increasing relative effectiveness in an emergency department

Contact tracing is the systematic method of identifying individuals potentially exposed to infectious diseases. Electronic medical record (EMR) use for contact tracing is time-consuming and may miss exposed individuals. Real-time location systems (RTLSs) may improve contact identification. Therefore, the relative effectiveness of these 2 contact tracing methodologies were evaluated. During a pertussis outbreak in the United States, a retrospective case study was conducted between June 14 and August 31, 2016, to identify the contacts of confirmed pertussis cases, using EMR and RTLS data in the emergency department of a tertiary care medical center. Descriptive statistics and a paired t test (α = 0.05) were performed to compare contacts identified by EMR versus RTLS, as was correlation between pertussis patient length of stay and the number of potential contacts. Nine cases of pertussis presented to the emergency department during the identified time period. RTLS doubled the potential exposure list (P < .01). Length of stay had significant positive correlation with contacts identified by RTLS (ρ = 0.79; P = .01) but not with EMR (ρ = 0.43; P = .25). RTLS doubled the potential pertussis exposures beyond EMR-based contact identification. Thus, RTLS may be a valuable addition to the practice of contact tracing and infectious disease monitoring.

Assessment of clinical symptoms in household contacts of confirmed pertussis cases

We assessed the value of the clinical symptoms included in the case definition of pertussis in household contacts of laboratory-confirmed cases. A prospective epidemiological study was made in two Spanish regions. Household contacts were identified for each confirmed case reported during 2012 and 2013. Two clinical samples were taken to determine the presence or absence of Bordetella pertussis by culture or real-time PCR. Clinical variables, age and vaccination status were recorded. Positive and negative likelihood ratios (PLR, NLR) were estimated for each symptom. 2852 household contacts of 688 confirmed cases were reported. 178 household contacts with clinical symptoms were analyzed: 150 were laboratory confirmed and 28 were not. The clinical symptom with the highest PLR in comparison with the NLR was paroxysmal cough(PLR 4.76; 95% CI 1.91-11.87 and NLR 0.37; 95% CI 0.28-0.49). The contrast between the PLR and NLR was especially important for persons aged <18 years (PLR 7.08; 95% CI 1.10-45.74 and NLR 0.32; 95% CI 0.21-0.49). The clinical symptoms of pertussis are poor predictors of pertussis disease, independently of the vaccination status. Differences were observed between persons aged <18 years and adults. To adopt the appropriate treatment and control measures, rapid laboratory confirmation by PCR of all household contacts of confirmed cases who present any clinical symptoms compatible with pertussis should be recommended.

How well do ICD-9 physician claim diagnostic codes identify confirmed pertussis cases in Alberta, Canada? A Canadian Immunization Research Network (CIRN) Study

BackgroundRates of Bordetella pertussis have been increasing in Alberta, Canada despite vaccination programs. Waning immunity from existing acellular component vaccines may be contributing to this. Vaccine effectiveness can be estimated using a variety of data sources including diagnostic codes from physician billing claims, public health records, reportable disease and laboratory databases. We sought to determine if diagnostic codes from billing claims (administrative data) are adequately sensitive and specific to identify pertussis cases among patients who had undergone disease-specific laboratory testing.MethodsData were extracted for 2004–2014 from a public health communicable disease database that contained data on patients under investigation for B. pertussis (both those who had laboratory tests and those who were epidemiologically linked to laboratory-confirmed cases) in Alberta, Canada. These were deterministically linked using a unique lifetime person identifier to the provincial billing claims database, which contains International Classification of Disease version 9 (ICD-9) diagnostic codes for physician visits. We examined visits within 90 days of laboratory testing. ICD-9 codes 033 (whooping cough), 033.0 (Bordetella pertussis), 033.1 (B. parapertussis), 033.8 (whooping cough, other specified organism), and 033.9 (whooping cough, other unspecified organism) in any of the three diagnostic fields for a claim were classified as being pertussis-specific codes. We calculated sensitivity, specificity, positive (PPV) and negative (NPV) predictive values.ResultsWe identified 22,883 unique patients under investigation for B. pertussis. Of these, 22,095 underwent laboratory testing. Among those who had a laboratory test, 2360 tested positive for pertussis. The sensitivity of a pertussis-specific ICD-9 code for identifying a laboratory-confirmed case was 38.6%, specificity was 76.9%, PPV was 16.0%, and NPV was 91.6%.ConclusionICD-9 codes from physician billing claims data have low sensitivity and moderate specificity to identify laboratory-confirmed pertussis among persons tested for pertussis.

Reduced Severity of Pertussis in Persons With Age-Appropriate Pertussis Vaccination-United States, 2010-2012.

In 2012, >48000 pertussis cases were reported in the United States. Many cases occurred in vaccinated persons, showing that pertussis vaccination does not prevent all pertussis cases. However, pertussis vaccination may have an impact on disease severity. We analyzed data on probable and confirmed pertussis cases reported through Enhanced Pertussis Surveillance (Emerging Infections Program Network) between 2010 and 2012. Surveillance data were collected through physician and patient interview and vaccine registries. We assessed whether having received an age-appropriate number of pertussis vaccines (AAV) (for persons aged ≥3 months) was associated with reduced odds of posttussive vomiting, a marker of more clinically significant illness, or of severe pertussis (seizure, encephalopathy, pneumonia, and/or hospitalization). Adjusted odds ratios were calculated using multivariable logistic regression. Among 9801 pertussis patients aged ≥3 months, 77.6% were AAV. AAV status was associated with a 60% reduction in odds of severe disease in children aged 7 months-6 years in multivariable logistic regression and a 30% reduction in odds of posttussive vomiting in persons aged 19 months-64 years. Serious pertussis symptoms and complications are less common among AAV pertussis patients, demonstrating that the positive impact of pertussis vaccination extends beyond decreasing risk of disease.

Pertussis incidence rates in Novi Sad (Serbia) before and during improved surveillance

Introduction/Objective. The Global Pertussis Initiative (GPI) proposed clinical case definitions for pertussis diagnosis in three different age cohorts in order to improve surveillance of pertussis especially in older children, adolescents, and adults. The main goal of this research was to compare the burden of pertussis in the city of Novi Sad before and after the introduction of improved surveillance using the GPI clinical case definitions of pertussis. Methods. Baseline data on pertussis were obtained from routine (non-sentinel) reporting before improved surveillance was introduced. From September 16, 2012, clinical case definitions proposed by GPI were applied within improved (sentinel and hospital) surveillance, while surveillance clinical case definitions were not introduced within non-sentinel. To confirm the suspected diagnosis, sampling of nasopharyngeal swab and/or blood was obtained from all cases. The choice of laboratory method (PCR or ELISA) depended on the duration of coughing and the age of the patients. Data were statistically processed by SPSS Statistics, version 22. Results. During the 12-year period before the introduction of improved surveillance, only two clinical pertussis cases were registered. In contrast, during the two-year period of improved surveillance, a total of 14 (season 2012/13) and 146 (season 2013/2014) confirmed pertussis cases were reported. Significant differences were determined in distribution of pertussis according to the type of surveillance and the level of health care. Conclusion. Introduction of clinical case definitions proposed by GPI improved the quality of surveillance and enabled an insight in the distribution of pertussis in all age groups and at all levels of health care.

Using Spatial Analysis to Inform Community Immunization Strategies.

Introduction:Recent pertussis outbreaks in the United States suggest our response to local disease outbreaks (eg, vaccine-preventable Bordetella pertussis) may benefit from understanding and applying spatial analytical methods that use data from immunization information systems at a subcounty level.Methods:A 2012 study on Denver, CO, residents less than 19 years of age confirmed pertussis cases and immunization information system records were geocoded and aggregated to the census tract (CT) level. An algorithm assessed whether individuals were up-to-date (UTD) for pertussis vaccines. Pearson, Spearman, and Kendall correlations assessed relations between disease incidence and pertussis vaccine coverage. Using spatial analysis software, disease incidence and UTD rates were spatially weighted, and smoothed. Global and local autocorrelations based on univariate Moran’s I spatial autocorrelation statistics evaluated whether a CT’s rate belong to a cluster based on incidence or UTD measures.Results:Overall disease incidence rate was 116.8/100 000. Assessment of pertussis vaccination coverage was available for 90% of the population. Among 134 672 Denver residents less than 19 years old, 103 496 (77%) were UTD for pertussis vaccines. Raw correlation coefficients showed weak relationships between incidence and immunization rates due to the presence of outliers. With geospatial and clustering analysis, estimates and correlation coefficients were improved with statistically significant Moran’s I values for global and local autocorrelations rejecting the null hypothesis that incidence or UTD rates were randomly distributed. With evidence indicating the presence of clusters, smoothed and weighted disease incidence and UTD rates in 144 CTs identified 21 CTs (15%) for potential public health intervention.Conclusions:Correlation of raw disease incidence and vaccine UTD rates in subcounty regions showed limited association, providing limited information for decision making. By assessing for clusters using spatial analysis methods, we identified CTs with higher incidence and lower immunization coverage for targeted public health interventions.

Comparing Seasonal Pattern of Laboratory Confirmed Cases of Pertussis with Clinically Suspected Cases

ObjectivesDuring recent decades, there has been limited attention on the seasonal pattern of pertussis within a high vaccine coverage population. This study aimed to compare the seasonal patterns of clinical suspected pertussis cases with those of laboratory confirmed cases in Iran. MethodsThe current study was conducted using time series methods. Time variables included months and seasons during 2011–2013. The effects of seasons and months on the incidence of pertussis were estimated using analysis of variance or Kruskal–Wallis. ResultsThe maximum average incidence of clinically confirmed pertussis was 23.3 in July (p = 0.04), but the maximum incidence of clinical suspected pertussis was 115.7 in May (p = 0.6). The maximum seasonal incidences of confirmed and clinical pertussis cases were reported in summer (average: 12, p = 0.004), and winter (average: 108.1; p = 0.4), respectively. ConclusionThe present study showed that the seasonal pattern of laboratory confirmed pertussis cases is highly definite and different from the pattern of clinical suspected cases.

Investigation of Pertussis Cases in a Texas County, 2008-2012.

Within the past 25 years, there has been a dramatic increase in the incidence of pertussis cases in the United States. As such, this investigation reports on the high-risk groups and describes risk factors of pertussis cases in a large Texas county. This study was a cross-sectional analysis of data collected by health department employees using the Texas Department of State Health Service's Pertussis Case Track Record, which is the standard investigation form for collecting vital information on pertussis cases. We extracted and analyzed county-level data for a 5-year period (2008-2012). The study population at risk included all current residents in this county, and cases included all who were clinically diagnosed as having confirmed or probable pertussis cases that were reported to the health department according to the Centers for Disease Control and Prevention case definition. The vaccination status of a case was defined as fully vaccinated, partially vaccinated, or not vaccinated. A total of 198 probable and confirmed pertussis cases were included in this analysis. Most of the cases were infants younger than 1 year old (n = 107). The largest category of cases was not vaccinated and of the rest, 32.8% were partially vaccinated, 17.2% had unknown vaccination status, and 13.1% were fully vaccinated. Only 48 (24.2%) sources of exposure were identified and they included fathers (14.6%), sisters (14.6%), brothers (14.6%), other children (14.6%), and mothers (12.5%). Many sources of exposure (n = 26, 54.1%) were unaware of their vaccination history. Hispanics accounted for 84.5% of cases in the younger than 1 year old group and 88.9% of cases were in the 1 to 2 years old group. With respect to race/ethnicity and vaccination status of the cases, 39.46% of Hispanics, 32% of whites, and 50% of blacks were reported to be unvaccinated. Increasing pertussis vaccination coverage among children, as well as providing booster shots to adults with special attention on the Hispanic population, may prove to be an effective strategy for health departments.