Pertussis Transmission Research Articles

Whooping cough dynamics in Chile (1932-2010): disease temporal fluctuations across a north-south gradient.

BackgroundThe spatial-temporal dynamics of Bordetella pertussis remains as a highly interesting case in infectious disease epidemiology. Despite large-scale vaccination programs in place for over 50 years around the world, frequent outbreaks are still reported in many countries.MethodsHere, we use annual time series of pertussis incidence from the thirteen different regions of Chile (1952–2010) to study the spatial-temporal dynamics of Pertussis. The period 1975–1995 was characterized by a strong 4 year cycle, while the last two decades of the study period (1990–2010) were characterized by disease resurgence without significant periodic patterns.ResultsDuring the first decades, differences in periodic patterns across regions can be explained by the differences in susceptible recruitment. The observed shift in periodicity from the period 1952–1974 to the period 1975–1995 across regions was relatively well predicted by the susceptible recruitment and population size. However, data on vaccination rates was not taken into account in this study.ConclusionsOur findings highlight how demography and population size have interacted with the immunization program in shaping periodicity along a unique latitudinal gradient. Widespread B. pertussis vaccination appears to lead to longer periodic dynamics, which is line with a reduction in B. pertussis transmission, but our findings indicate that regions characterized by both low birth rate and population size decreased in periodicity following immunization efforts.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-015-1292-2) contains supplementary material, which is available to authorized users.

Bordetella pertussis transmission.

Bordetella pertussis and B. bronchiseptica are Gram-negative bacterial respiratory pathogens. Bordetella pertussis is the causative agent of whooping cough and is considered a human-adapted variant of B. bronchiseptica. Bordetella pertussis and B. bronchiseptica share mechanisms of pathogenesis and are genetically closely related. However, despite the close genetic relatedness, these Bordetella species differ in several classic fundamental aspects of bacterial pathogens such as host range, pathologies and persistence. The development of the baboon model for the study of B. pertussis transmission, along with the development of the swine and mouse model for the study of B. bronchiseptica, has enabled the investigation of different aspects of transmission including the route, attack rate, role of bacterial and host factors, and the impact of vaccination on transmission. This review will focus on B. pertussis transmission and how animal models of B. pertussis transmission and transmission models using the closely related B. bronchiseptica have increased our understanding of B. pertussis transmission.

Examining the role of different age groups, and of vaccination during the 2012 Minnesota pertussis outbreak.

There is limited information on the roles of different age groups during pertussis outbreaks. Little is known about vaccine effectiveness against pertussis infection (both clinically apparent and subclinical), which is different from effectiveness against reportable pertussis disease, with the former influencing the impact of vaccination on pertussis transmission in the community. For the 2012 pertussis outbreak in Minnesota, we estimated odds ratios for case counts in pairs of population groups before vs. after the epidemic’s peak. We found children aged 11–12y, 13–14y and 8–10y experienced the greatest rates of depletion of susceptible individuals during the outbreak’s ascent, with all ORs for each of those age groups vs. groups outside this age range significantly above 1, with the highest ORs for ages 11–12y. Receipt of the fifth dose of DTaP was associated with a decreased relative role during the outbreak’s ascent compared to non-receipt [OR 0.16 (0.01, 0.84) for children aged 5, 0.13 (0.003, 0.82) for ages 8–10y, indicating a protective effect of DTaP against pertussis infection. No analogous effect of Tdap was detected. Our results suggest that children aged 8–14y played a key role in propagating this outbreak. The impact of immunization with Tdap on pertussis infection requires further investigation.

Understanding Trends in Pertussis Incidence: An Agent-Based Model Approach.

We examined the impact of undetected infections, adult immunity, and waning vaccine-acquired immunity on recent age-related trends in pertussis incidence. We developed an agent-based model of pertussis transmission in Dakota County, Minnesota using case data from the Minnesota Department of Health. For outbreaks in 2004, 2008, and 2012, we fit our model to incidence in 3 children's age groups relative to adult incidence. We estimated parameters through model calibration. The duration of vaccine-acquired immunity after completion of the 5-dose vaccination series decreased from 6.6 years in the 2004 model to approximately 3.0 years in the 2008 and 2012 models. Tdap waned after 2.1 years in the 2012 model. A greater percentage of adults were immune in the 2008 model than in the 2004 and 2012 models. On average, only 1 in 10 adult infections was detected, whereas 8 in 10 child infections were detected. The observed trends in relative pertussis incidence in Dakota County can be attributed in part to fluctuations in adult immunity and waning vaccine-acquired immunity. No single factor accounts for current pertussis trends.

Mathematical modeling of delayed pertussis vaccination in infants

Pertussis is an acute vaccine-preventable respiratory disease that remains a public health problem. In an attempt to improve the control of the disease, many countries have incorporated new boosters in their vaccination schedule. Since the incorporation of these boosters is relatively recent, there are not enough data about their impact to support and/or universalize their use. Alternative strategies such as the improvement in vaccine coverage and reduction in vaccination delays, in addition to the incorporation of boosters, could be implemented. Though these strategies are not new, they have not been adequately evaluated in order to be implemented and/or prioritized. To evaluate the potential impact of these alternative strategies on pertussis incidence, we developed a methodology that involves the use of data collected from vaccination centers and an age-structured deterministic mathematical model for pertussis transmission. The results obtained show that strategies that avoid delays in vaccination have a strong impact on incidence reduction in the most vulnerable population (infants less than 1y). In regions with high vaccination coverage (95%) the elimination of delays in the three primary doses decreases pertussis incidence in infants by approximately 20%. In regions where delays in the administration of vaccines are higher, the combined action to reduce delays and improve coverage leads to a significant improvement in disease control in infants. By repeating the calculations using different sets of parameters that describe different possible epidemiologic scenarios, we determined the robustness of our results.All the results presented highlight the importance of having high vaccine coverage and shorter delays in vaccine administration in order to reduce the impact of the disease in infants.

Strategies to decrease pertussis transmission to infants.

The Global Pertussis Initiative (GPI) is an expert scientific forum addressing the worldwide burden of pertussis, which remains a serious health issue, especially in infants. This age cohort is at risk for developing pertussis by transmission from those in close proximity. Risk is increased in infants aged 0 to 6 weeks, as they are too young to be vaccinated. Older infants are at risk when their vaccination schedules are incomplete. Infants also bear the greatest disease burden owing to their high risk for pertussis-related complications and death; therefore, protecting them is a high priority. Two vaccine strategies have been proposed to protect infants. The first involves vaccinating pregnant women, which directly protects through the passive transfer of pertussis antibodies. The second strategy, cocooning, involves vaccinating parents, caregivers, and other close contacts, which indirectly protects infants from transmission by preventing disease in those in close proximity. The goal of this review was to present and discuss evidence on these 2 strategies. Based on available data, the GPI recommends vaccination during pregnancy as the primary strategy, given its efficacy, safety, and logistic advantages over a cocoon approach. If vaccination during pregnancy is not feasible, then all individuals having close contact with infants <6 months old should be immunized consistent with local health authority guidelines. These efforts are anticipated to minimize pertussis transmission to vulnerable infants, although real-world effectiveness data are limited. Countries should educate lay and medical communities on pertussis and introduce robust surveillance practices while implementing these protective strategies.

Dynamics of Pertussis Transmission in the United States.

Past patterns of infectious disease transmission set the stage on which modern epidemiologic dynamics are played out. Here, we present a comprehensive account of pertussis (whooping cough) transmission in the United States during the early vaccine era. We analyzed recently digitized weekly incidence records from Morbidity and Mortality Weekly Reports from 1938 to 1955, when the whole-cell pertussis vaccine was rolled out, and related them to contemporary patterns of transmission and resurgence documented in monthly incidence data from the National Notifiable Diseases Surveillance System. We found that, during the early vaccine era, pertussis epidemics in US states could be categorized as 1) annual, 2) initially annual and later multiennial, or 3) multiennial. States with predominantly annual cycles tended to have higher per capita birth rates, more household crowding, more children per family, and lower rates of school attendance than the states with multiennial cycles. Additionally, states that exhibited annual epidemics during 1938-1955 have had the highest recent (2001-2010) incidence, while those states that transitioned from annual cycles to multiennial cycles have had relatively low recent incidence. Our study provides an extensive picture of pertussis epidemiology in the United States dating back to the onset of vaccination, a back-story that could aid epidemiologists in understanding contemporary transmission patterns.

Effectiveness and acceptance of a health care-based mandatory vaccination program.

To decrease the risk of transmission of hospital-associated transmission of influenza and pertussis through mandatory vaccination of staff. A mandatory influenza and toxoid-diphtheria toxoid-acellular pertussis program was implemented systemwide. A structured vaccine exemption program was implemented for those requesting a medical and/or religious/moral/ethical exemption. Systemwide influenza vaccination rates increased from 67% historically, 76.2% in the 2012 to 2013 influenza season, to 94.7% in 2013 to 2014 with an overall compliance rate of 97.8%. Toxoid-diphtheria toxoid-acellular pertussis vaccination rates systemwide reached 94.9%, with an overall compliance rate of 98%. Higher rates were experienced at individual hospital facilities compared with the corporate location. Successful vaccination campaign outcomes can be achieved through diligent enforcement of mandatory vaccination, masking, and other infection prevention procedures.

Shortcomings of pertussis vaccines: why we need a third generation vaccine

First generation whole-cell (wP) and second generation acellular (aP) pertussis vaccines have been highly effective in preventing childhood deaths due to pertussis, yet both vaccines have drawbacks that have limited their long-term usefulness. These include issues of reactogenicity and potency in the case of wP, and limited durability of protection and the potential for selection of escape mutants in the case of aP. Neither vaccine prevents disease in neonatal infants who continue to die from pertussis. A third generation of pertussis vaccines that provides broad, durable protection is needed. In the meantime, countries using wP should continue to do so, while countries using aP need to consider policies and schedules that reduce pertussis transmission to unvaccinated infants. In this respect, maternal vaccination appears to be a promising solution.

Preventing the Spread of Pertussis in Pediatric Healthcare Settings.

The surge in pertussis incidence in recent years underscores a critical need for effective plans to prevent transmission in pediatric healthcare settings. Adolescents and adults are common sources of infection for unimmunized or incompletely immunized infants and children with waning immunity. Despite documented outbreaks being limited in size, pertussis poses a threat to pediatric healthcare facilities due to the risk for widespread transmission, potentially severe complications among vulnerable patient populations, and high outbreak control-related costs. Healthcare personnel, visitors, and parents have been identified as sources of outbreaks, underscoring the importance of coordinated efforts to prevent transmission in these settings. This comprehensive review demonstrates that the risk of pertussis transmission in pediatric healthcare settings warrants heightened focus on strategies to recognize disease earlier, improve diagnostic evaluation, and facilitate effective contact tracing and post-exposure prophylaxis measures. This review suggests that healthcare personnel can play a significant role in the prevention of healthcare-associated pertussis.

Barriers to the Use of PPE to Prevent Pertussis Exposures in a Pediatric Primary Care Network.

The resurgence of pertussis is contributing to mounting healthcare worker (HCW) exposures, especially within pediatric outpatient settings. Infection prevention and control (IPC) guidelines for ambulatory sites exist, but are not uniformly implemented. Our aim was to identify facilitators and barriers to the use of IPC practices to prevent pertussis transmission in ambulatory pediatric settings. HCWs at 18 of 25 (72%) clinics in a pediatric ambulatory network completed a theory-based questionnaire about pertussis and personal protective equipment (PPE). The questionnaire contained randomly distributed versions of two vignettes to create an experimental design assessing barriers to PPE use. Three hundred forty-three of 467 (73%) HCWs completed the survey: 234 (68%) clinical and 109 (32%) nonclinical. Seventy-one percent of clinical HCWs reported wearing PPE when caring for a patient with suspected pertussis; only 27% used PPE for patients with any respiratory symptoms. Among clinical HCWs, reported PPE use when caring for patients with suspected pertussis was independently associated with attitudes toward PPE (odds ratio [OR] 5.4, 95% confidence interval [CI] 1.8, 16.6), knowledge and skills (OR 4.6, 95% CI 1.4, 15.2), and lack of perceived barriers (OR 3.2, 95% CI 1.3, 7.9). HCWs who did not perceive PPE use as a norm were less likely to report using PPE (OR 0.2, 95% CI 0.1, 0.6) or distributing masks to patients with cough (OR 0.02, 95% CI 0.00, 0.2). Reported PPE use was not influenced by perceived infection risk or mask accessibility. Our results identified barriers to PPE use and targets for education to prevent pertussis transmission in ambulatory pediatric settings.

Reply to Domenech de Cellès et al.: Infection and transmission of pertussis in the baboon model

We developed a nonhuman primate model to study whether pertussis vaccination is able to disrupt Bordetella pertussis colonization and transmission, and demonstrated that baboons vaccinated with the acellular pertussis vaccines (aP) were protected from classic pertussis symptoms (i.e., coughing and leukocytosis) but were highly colonized and transmitted pertussis to contacts in two of two experiments (1). In their letter to the editor, Domenech de Celles et al. question our extrapolation of results from the baboon model to transmission in human populations (2). We agree that these data should not be directly extrapolated to pertussis transmission in humans. Although baboons are >96% genetically similar to humans, there are likely differences in how the species respond to vaccination and infection. We also agree that aP-vaccinated infected people are likely less efficient at transmitting pertussis compared with unvaccinated infected people, although it is not clear to what extent. In our model, the time required for transmission was greater when the infected baboon was aP-vaccinated compared with unvaccinated animals (3). However, in the baboon model, aP did not prevent infection as well as whole-cell vaccine (wP); therefore, it is reasonable to conclude that circulation of B. pertussis will be higher in an aP-vaccinated population than in a wP-vaccinated population.

Prolonged Pertussis Outbreak in Ontario Originating in an Under-immunized Religious Community.

A prolonged pertussis outbreak began in Ontario in November 2011 in an under-immunized religious community and subsequently spread to the general population and a second religious community in the same region of the province. To compare the epidemiology in the religious communities to that of the general population within the affected jurisdictions. The analysis includes cases reported through the integrated Public Health Information System (iPHIS) between November 1, 2011 and April 15, 2013 that met the outbreak case definition. Health unit staff assessed whether cases were members of religious communities through case investigations and collected information on immunization status, treatment and outcomes. A total of 443 confirmed and probable outbreak cases were reported in 7 health units. The outbreak began in one religious community (138 cases), before spreading to the general population in the region (273 cases). A second under-immunized community within the region experienced 32 cases. Thirteen cases were hospitalized and no deaths were reported. Disease peaked earlier in the religious community; cases were significantly younger, more likely to be at high risk for pertussis and more likely to be unimmunized. Among the fully immunized general population, 51% of cases were between 10-14 years and with a median of 5.6 years since their last immunization. The epidemiology of pertussis in the under-immunized community is distinct from the general population. Transmission of pertussis to the general community is not unexpected during an outbreak; however, the proportion of cases up to date with immunization warrants further investigation.

Estimation of the Underlying Burden of Pertussis in Adolescents and Adults in Southern Ontario, Canada

Despite highly successful vaccination programs and high vaccine uptake, both endemic pertussis and periodic pertussis outbreaks continue to occur. The under-recognized role of adolescents and adults in disease transmission, due to waning immunity following natural infection and vaccination, and reduced likelihood of correct diagnosis, may contribute to pertussis persistence. We constructed a mathematical model to describe the transmission of pertussis in Southern Ontario in both pre-vaccine and vaccine eras, to estimate the underlying burden of pertussis in the population. The model was well calibrated using the best available data on pertussis in the pre-vaccination (1880–1929) and vaccination (1993–2004) eras in Ontario. Pertussis under-reporting by age group was estimated by comparing model-projected incidence to reported laboratory-confirmed cases for Greater Toronto. Best-fit model estimates gave a basic reproductive number of approximately 10.6, (seasonal range 9.9 to 11.5). Under-reporting increased with age, and approximately >95% of infections in children were caused by infections in persons with waning immunity to pertussis following prior infection or vaccination. A well-calibrated model suggests that under-recognized cases of pertussis in older individuals are likely to be an important driver of ongoing pertussis outbreaks in children. Model projections strongly support enhancement of booster vaccination efforts in adults.

Can vaccine legacy explain the British pertussis resurgence?

Pertussis incidence has been rising in some countries, including the UK, despite sustained high vaccine coverage. We questioned whether it is possible to explain the resurgence without recourse to complex hypotheses about pathogen evolution, subclinical infections, or trends in surveillance efficiency. In particular, we investigated the possibility that the resurgence is a consequence of the legacy of incomplete pediatric immunization, in the context of cohort structure and age-dependent transmission. We constructed a model of pertussis transmission in England and Wales based on data on age-specific contact rates and historical vaccine coverage estimates. We evaluated the agreement between model-predicted and observed patterns of age-specific pertussis incidence under a variety of assumptions regarding the duration of immunity. Under the assumption that infection-derived immunity is complete and lifelong, and regardless of the duration of vaccine-induced immunity, the model consistently predicts a resurgence of pertussis incidence comparable to that which has been observed. Interestingly, no resurgence is predicted when infection- and vaccine-derived immunities wane at the same rate. These results were qualitatively insensitive to rates of primary vaccine failure. We conclude that the alarming resurgence of pertussis among adults and adolescents in Britain and elsewhere may simply be a legacy of historically inadequate coverage employing imperfect vaccines. Indeed, we argue that the absence of resurgence at this late date would be more surprising. Our analysis shows that careful accounting for age dependence in contact rates and susceptibility is prerequisite to the identification of which features of pertussis epidemiology want additional explanation.

KRZTUSIEC JAKO CHOROBA ZAKAŹNA PRACOWNIKÓW OCHRONY ZDROWIA - PRZYPADEK KLINICZNY Z KOMENTARZEM

We discuss the changing epidemiological situation of pertussis observed in recent years, with a focus on the shift of cases from young children to older age groups, teenagers and adults. Whooping cough may affect healthcare workers who belong to a high-risk group and cause hospital infections. We present a case report of pertussis in a nurse and the recommended prophylactic measures in healthcare workers. The current definition and diagnosis of pertussis is also discussed. The clinical course of pertussis can be significantly alleviated and highly non-specific, with no typical coughing and vomiting in people vaccinated against whooping cough a few years earlier. Pertussis should be considered in the differential diagnosis of cough lasting more than fourteen days. Improvement of the epidemiological situation requires, besides immunization of infants, regular and universal booster immunization for adolescents and adults. Vaccinations for health care workers of neonatal and pediatric wards are recommended in the National Program of Immunization for 2013. It seems that booster vaccination of health care workers with a triple vaccine against diphtheria, tetanus and acellular pertussis (dTpa) of the reduced quantity of antigens, particularly of health workers caring for infants, children and the elderly, may be the most effective way to reduce the risk of pertussis transmission in the health care environment.

Bias in Pertussis Incidence Data and Its Implications for Public Health Epidemiology

A fter a decline of more than 99% from 1934 to 1976, pertussis incidence in the United States has increased dramatically over the last 3 decades. Although the initial decrease was attributed to the introduction of vaccination programs, the muchpublicized recent resurgence has occurred despite continued high-vaccination uptake estimates.4 Unfortunately, an incomplete understanding both of the underlying factors causing this resurgence in incidence and of the key drivers of pertussis transmission in general confounds creation of effective vaccination strategies and public health responses. A powerful approach to dissecting and elucidating the relative contributions of these drivers is the development of disease transmission models and their confrontation—via statistical inference methodology—with highly resolved incidence data. Despite the existence of highly resolved data collected through the Supplementary Pertussis Surveillance System (SPSS), and generous stated policy guidelines regarding data sharing/release, these data are not publicly accessible for researchers. Here, we discuss the lack of resolution and important biases in the incidence reports that are publicly available and argue in favor of more transparency in data sharing policies and broader dissemination of incidence data such as those collated through the SPSS. In addition to mortality and morbidity, the public health consequences of pertussis include an economic burden from lost productivity, as well as financial expenditures in areas such as associated medical costs, public awareness campaigns, and increased vaccinations. The most significant increase in pertussis in the United States (and other developed countries with vaccine programs) has occurred among adolescents and adults, with smaller increases observed for infants and older children. Nonetheless, infants make up the plurality of reported cases and nearly all of the fatalities,

Detection of the Presence of Bordetella pertussis by Real-Time Polymerase Chain Reaction in Children Diagnosed with Pertussis and among their Household Contacts

Background: Despite high vaccination coverage, pertussis continues to be a great public health problem. Adults and adolescents are source of infection for infants who are too young to be completely vaccinated. The aim of the study is detect if there is a household transmission of pertussis. Methods: Presence of Bordetella pertussis among the household contacts of the children who had had the positive result for Bordetella pertussis by real-time polymerase chain reaction was detected. Results: Of the 173 infants with clinical suspicion of pertussis, 48 (27.7%) turned out to be positive by PCR. The mothers of 19 (41.3% of all tested mothers) of them were also PCR positive for B. pertussis, being the family member most frequently infected. Conclusion: Despite high coverage of pertussis vaccination in Turkey, pertussis is prevalent both in incompletely protected infants and older children. High rate of presence of the bacteria in the household contacts depicts the importance of further pertussis booster vaccination in adolescents, adults and the targeted vaccination of the adults having close contacts with infants (cocoon strategy).

Pertussis and Persistent Cough: Practical, Clinical and Epidemiologic Issues

BackgroundEpidemiologic issues of testing, treatment, prevention, immunization, mandated reporting, and post-exposure prophylaxis do not often intrude on the Emergency Department management of the well-appearing adolescent or adult with a couple of weeks of cough. ObjectivesConsidering that waning immunity to pertussis, the only vaccine-preventable disease with increasing cases and deaths in the United States, is responsible for 12–35% of such illness, such issues need to be considered. DiscussionMostly self-limited in adults, transmission of pertussis to infants places them at risk for hospitalization and death. Pertussis is highly contagious (80% transmission), and atypical presentations are the rule in adults (cough alone) and infants (apnea, bradycardia, poor feeding). Treatment in the first few weeks can impact the clinical course, and later treatment can still prevent transmission. Clinical features like paroxysmal cough, inspiratory “whoop,” and post-tussive emesis have mildly increased predictive values and may be absent in adults. Testing is unreliable after 3 weeks of cough. Treatment reduces communicability within 5 days and is suggested without regard to test results within 3 weeks of cough onset for those aged > 1 year (within 6 weeks of cough for < 1 year). Reporting requirements are based on the clinical case definition: ([Cough ≥2 weeks] + [paroxysms OR whoop OR post-tussive emesis]). Lower reporting thresholds are appropriate during an outbreak or when vulnerable populations are at risk. Post-exposure prophylaxis is recommended for at-risk contacts. Tdap is encouraged for all adults. ConclusionPractical recommendations consistent with the most current guidelines are offered.

Estimation of Household Transmission Rates of Pertussis and the Effect of Cocooning Vaccination Strategies on Infant Pertussis

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. 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. 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. 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.