Adult pertussis is unrecognized public health problem in Thailand

Seroepidemiological Assessment of Bordetella pertussis in Jahrom, Southern Iran: A Cross-Sectional Study

Background

Bordetella pertussis, the causative agent of whooping cough, is a significant contributor to recurrent persistent cough across all age groups, including vaccinated individuals. This seroepidemiological study aims to address the gap in understanding pertussis incidence by investigating its occurrence in individuals with persistent cough and describing the characteristics of affected patients admitted to clinical centers in Jahrom, Southwest Iran.

Methods

This cross-sectional study enrolled 110 patients with a cough persisting for at least 2 weeks, admitted to clinical centers in Jahrom, Iran. Blood samples were collected at baseline and on day 21 of follow-up. Serum samples were analyzed for anti-pertussis toxin immunoglobulin G (anti-PT-IgG) levels using an enzyme-linked immunosorbent assay. Demographic factors, including age, gender, occupation, area of residence, and family size, were also evaluated.

Results

Among the 110 participants, 77 (70%) were female, and seven patients (6.4%) tested seropositive for anti-PT-IgG. No significant associations were observed between pertussis incidence and the analyzed variables, including age, gender, occupation, area of residence (urban vs. rural), and family size (p > 0.05). These findings underscore the importance of enhancing vaccination coverage to reduce the prevalence of B. pertussis in the community.

Conclusion

This study highlights the occurrence of pertussis in individuals presenting solely with a persistent cough, absent of classic symptoms. The findings emphasize the need for healthcare providers to conduct detailed assessments and utilize rapid diagnostic methods for timely detection. This is particularly crucial in regions with high vaccination rates but limited awareness of pertussis recurrence.

Public health management of pertussis in adults: Practical challenges and future strategies

A panel of 24 international experts met in July 2022 to discuss challenges associated with pertussis detection, monitoring, and vaccination in adults; conclusions from this meeting are presented. There has been a shift in the epidemiology of pertussis toward older children and adults. This shift has been attributed to the waning of infection- or vaccine-induced immunity, newer detection techniques causing detection bias, and possibly the replacement of whole-cell pertussis with acellular vaccines in high-income countries, which may lead to immunity waning more quickly. The burden of adult pertussis is still likely under-ascertained due to widespread under-recognition by healthcare professionals (HCPs), under-diagnosis, and under-reporting in this age group. Non-standardized testing guidance and varied case definitions have contributed to under-reporting. Key barriers to HCP engagement with the tetanus, diphtheria, and pertussis (Tdap) vaccine include low awareness, lack of time/funding, and lack of motivation due to low prioritization of Tdap.

Bordetella bronchiseptica and Bordetella pertussis: Similarities and Differences in Infection, Immuno-Modulation, and Vaccine Considerations

Bordetella pertussis and Bordetella bronchiseptica belong to the genus Bordetella, which comprises 14 other species. B. pertussis is responsible for whooping cough in humans, a severe infection in children and less severe or chronic in adults. These infections are restricted to humans and currently increasing worldwide. B. bronchiseptica is involved in diverse respiratory infections in a wide range of mammals. For instance, the canine infectious respiratory disease complex (CIRDC), characterized by a chronic cough in dogs. At the same time, it is increasingly implicated in human infections, while remaining an important pathogen in the veterinary field. Both Bordetella can evade and modulate host immune responses to support their persistence, although it is more pronounced in B. bronchiseptica infection. The protective immune responses elicited by both pathogens are comparable, while there are important characteristics in the mechanisms that differ. However, B. pertussis pathogenesis is more difficult to decipher in animal models than those of B. bronchiseptica because of its restriction to humans. Nevertheless, the licensed vaccines for each Bordetella are different in terms of formulation, route of administration and immune responses induced, with no known cross-reaction between them. Moreover, the target of the mucosal tissues and the induction of long-lasting cellular and humoral responses are required to control and eliminate Bordetella. In addition, the interaction between both veterinary and human fields are essential for the control of this genus, by preventing the infections in animals and the subsequent zoonotic transmission to humans.

Evaluation of serum anti-pertussis toxin IgA antibodies for the diagnosis of Bordetella pertussis infection in young children

BACKGROUND

The determination of serum anti-pertussis toxin (PT) IgG antibodies is recommended for the diagnosis and surveillance of pertussis. However, the diagnostic power of anti-PT IgG can be hampered by possible interference from previous vaccinations. We aim to assess if anti-PT IgA antibodies can be well induced by Bordetella pertussis (B. pertussis) infections in children, and their capacity to improve pertussis serodiagnosis.

METHODS

Serum samples from 172 hospitalized children younger than 10 years old with confirmed pertussis were tested. Pertussis was confirmed by culture, PCR and/or serology. Anti-PT IgA antibodies were determined with commercial ELISA kits.

RESULTS

Sixty-four (37.2 %) subjects had anti-PT IgA antibodies greater than or equal to 15 IU/ml, and 52 (30.2 %) of them had anti-PT IgA antibodies greater than or equal to 20 IU/ml. No children with negative anti-PT IgG (less than 40 IU/ml) were observed to have anti-PT IgA antibodies greater than or equal to 15 IU/ml. Of patients younger than one year of age, about 50 % had an IgA antibody response. Moreover, the proportion of subjects with anti-PT IgA antibodies greater than or equal to 15 IU/ml among PCR negative subjects was significantly higher than that among PCR positive subjects (76.9 % vs 35.5 %).

CONCLUSIONS

The determination of anti-PT IgA antibodies does not seem to have added value for the serodiagnosis of pertussis in children older than one year of age. However, for infants, determination of serum anti-PT IgA antibodies appears to be useful for the diagnosis of pertussis especially when PCR and culture are negative. The results should be interpreted with caution as the number of subjects included in this study was limited.

Cost-Utility Analysis of Universal Maternal Pertussis Immunisation in Thailand: A Comparison of Two Model Structures

OBJECTIVES

This study aimed to assess the cost-effectiveness of introducing universal maternal pertussis immunisation under the national vaccine programme in Thailand.

METHODS

We conducted a cost-utility analysis from a societal perspective to compare maternal vaccination with (1) TdaP vaccine, (2) Td vaccine and aP vaccine, and (3) Td vaccine only. We constructed two decision-tree models with Markov elements, each following a different clinical pathway, to allow us to examine structural uncertainty. Costs were converted to 2021 Thai Baht (THB) and a discount rate of 3% was applied to health and cost outcomes, with sensitivity analysis at 0% and 6%. Parameter uncertainty was investigated through deterministic and probabilistic sensitivity analysis, with expected value of perfect information analysis.

RESULTS

Maternal pertussis vaccination would avert 27 cases and up to one death per year. The incremental cost-effectiveness ratio (ICER) for adding aP to the maternal immunisation schedule is 2,184,025 THB/QALY and the ICER for replacing maternal Td vaccination with TdaP is 3,198,101 THB/QALY. Maternal pertussis vaccination only becomes favourable in the probabilistic sensitivity analysis at cost-effectiveness thresholds above 6,000,000 THB/QALY, far above the Thai threshold of 160,000 THB/QALY. If incidence is less than 397 cases per 100,000, maternal pertussis vaccination will not be cost-effective in Thailand, within the plausible range for vaccine effectiveness and probability of hospitalisation. Budget impact is dominated by vaccination costs, which represent 12% and 18% of the 2021 national vaccine programme budget for introducing aP vaccine or for switching Td with TdaP vaccine, respectively.

CONCLUSIONS

We have found that maternal pertussis immunisation is not cost-effective in Thailand. Although there may be substantial under-reporting of pertussis cases, comparison with hospital data suggests that most under-reported cases are not hospitalised and therefore have negligible impact on our results. However, considerations such as affordability and local manufacturing may also be important for national immunisation programme decision-making.

Pertussis in Asia: Recent country-specific data and recommendations

The Global Pertussis Initiative (GPI) Roundtable Meeting held in 2019, which preceded the COVID-19 pandemic, focused on the incidence, surveillance, and immunization practices for pertussis in the Asian region. Participants from China, India, Indonesia, Malaysia, Pakistan, Philippines, South Korea, Taiwan, and Thailand presented country-specific information on pertussis prevalence, diagnosis, surveillance, vaccine administration and schedules, maternal and neonatal disease rates, and policies and practice of vaccination during pregnancy. In recent years, many Asian countries have seen an increase in pertussis cases, although underreporting of the disease is a concern. Currently, most Asian countries have only passive surveillance for pertussis in place. There is a need for improved surveillance to determine the disease burden and justify vaccination policies and recommendations, such as essential vaccination, boosters, and vaccination during pregnancy. Better awareness of the disease in adolescents and adults is necessary, and infant and childhood vaccination schedules need to be improved in many countries. Differences between private versus public sector vaccination schedules and between whole-cell and acellular pertussis vaccines should continue to be examined. It can be anticipated that unmet needs in the prevention and management of pertussis will continue as the COVID-19 pandemic evolves and that key recommendations highlighted in this meeting report will be of ongoing importance.

Seroprevalence Study of Pertussis in Adults at Childbearing Age and Young Infants Reveals the Necessity of Booster Immunizations in Adults in China

In China, the vaccination strategy against pertussis is started from 3 months of age, with no booster dose used after the booster given at two years. Despite a high vaccination coverage, pertussis has been increasingly reported since the last decade. This study evaluates the prevalence of serum anti-pertussis toxin (PT) IgG antibodies in adults at childbearing age and infants before the age of primary immunization in Beijing, China. A total of 1175 serum samples randomly selected from individuals who attended an annual health examination at the Sixth Medical Center of the PLA General Hospital, Beijing, in 2019, was included. The geometric mean concentration (GMC) and median concentration of anti-PT IgG antibodies among adults aged 20–39 years were 3.81 IU/mL and 3.24 IU/mL, and the corresponding concentrations were 1.72 IU/mL and 1.43 IU/mL among infants under 3 months of age. The seroprevalence of PT IgG antibodies ≥ 40 IU/mL in adults and infants was 2.0% (15/735) and 1.1% (5/440). In total, 65.99% (485/735) of adults and 83.41% (367/440) of infants had non-detectable pertussis-specific antibodies (<5 IU/mL). Our results showed that the majority of adults at a reproductive age and young infants are vulnerable to pertussis, suggesting that booster vaccinations in adults should be considered in this country.

Hospital-based prospective study of pertussis in infants and close contacts in Tehran, Iran

Background

Pertussis remain a global health concern, especially in infants too young to initiate their vaccination. Effective vaccination and high coverage limit the circulation of the pathogen, yet duration of protection is limited and boosters are recommended during a lifetime. In Iran, boosters are given at 18 months and 6 years old using whole pertussis vaccines for which efficacy is not known, and pertussis surveillance is scant with only sporadic biological diagnosis. Burden of pertussis is not well understood and local data are needed.

Methods

Hospital-based prospective study implementing molecular laboratory testing in infants aged ≤6 months and presenting ≥5 days of cough associated to one pertussis-like symptom in Tehran. Household and non-household contact cases of positive infants were evaluated by comprehensive pertussis diagnosis (molecular testing and serology) regardless of clinical signs. Clinical evaluation and source of infection were described.

Results

A total of 247 infants and 130 contact cases were enrolled. Pertussis diagnosis result was obtained for 199 infants and 104 contact cases. Infant population was mostly < 3 months old (79.9%; 157/199) and unvaccinated (62.3%; 124/199), 20.1% (40/199) of them were confirmed having B. pertussis infection. Greater cough duration and lymphocyte counts were the only symptoms associated to positivity. Half of the contact cases (51.0%; 53/104) had a B. pertussis infection, median age was 31 years old. A proportion of 28.3% (15/53) positive contacts did not report any symptom. However, 67.9% (36/53) and 3.8% (2/53) of them reported cough at inclusion or during the study, including 20.8% (11/53) who started coughing ≥7 days before infant cough onset. Overall, only five samples were successfully cultured.

Conclusion

These data evidenced the significant prevalence of pertussis infection among paucy or poorly symptomatic contacts of infants with pertussis infection. Widespread usage of molecular testing should be implemented to identify B. pertussis infections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06266-6.

Immunological Distinctions between Acellular and Whole-Cell Pertussis Immunizations of Baboons Persist for at Least One Year after Acellular Vaccine Boosting

While both whole-cell (wP) and acellular pertussis (aP) vaccines have been highly effective at reducing the global pertussis disease burden, there are concerns that compared to wP vaccination, the immune responses to aP vaccination may wane more rapidly. To gain insights into the vaccine elicited immune responses, pre-adult baboons were immunized with either aP or wP vaccines, boosted with an aP vaccine, and observed over a nearly two-year period. Priming with a wP vaccine elicited a more Th17-biased response than priming with aP, whereas priming with an aP vaccine led to a more Th2-biased response than priming with wP. These differences were maintained after aP vaccine boost immunizations. Compared to aP, animals primed with a wP vaccine exhibited greater numbers of pertussis specific memory B cells. While aP and wP vaccine priming initially elicited similar levels of anti-pertussis toxin antibody, titers declined more rapidly in aP vaccine primed animals leading to a 4-fold difference. Both wP and aP vaccine immunization could induce serum bactericidal activity (SBA); however, only one wP vaccine immunization was required to elicit SBA while multiple aP vaccine immunizations were required to elicit lower, less durable SBA titers. In conclusion, when compared to aP vaccine, priming with wP vaccine elicits distinct cellular and humoral immune responses that persist after aP vaccine boosting.

Enhanced post-licensure safety surveillance of a new recombinant acellular pertussis vaccine licensed as a monovalent (aP, Pertagen®) and tetanus, reduced-dose diphtheria combination (TdaP, Boostagen®) vaccine for immunization of adolescents and adults in Thailand

A new generation of recombinant acellular pertussis vaccine containing genetically inactivated pertussis toxin (PTgen) was licensed as a monovalent pertussis vaccine (aP_gen; Pertagen®) and in combination with tetanus and reduced-dose diphtheria (TdaP_gen; Boostagen®) for active immunization in individuals aged 11 years and older in Thailand in 2016. We here report post-marketing safety data on the use of the vaccines in individuals in the community obtained through active pharmacovigilance surveillance including pregnant women participating in a prospective observational study. Between May 2017 and February 2020 for TdaP_gen and between June 2018 and February 2020 for aP_gen, participating health care providers vaccinated and collected safety data for 11,429 exposed adolescents and adults. This included 1778 pregnant women. The incidence rate of adverse events following immunization (AEFIs) was 11.5 per 1000 of vaccinated individuals (95% confidence interval (95% CI) 9.7-13.6). AEFIs mostly concerned local pain at the injection site and muscle pain, and symptoms were mild and mostly resolved within a few days with no complications. The incidence rate of AEFIs in women vaccinated during pregnancy was 1.1 per 1000 (95% CI 0.3-4.1). Of 833 pregnant women vaccinated with recombinant aP_gen or TdaP_gen, 91.4% (95% CI 89.3-93.3) had uncomplicated pregnancies and 98.7% (95% CI 97.7-99.4) of the 855 babies delivered by these women were born healthy, which exceeds rates generally reported in Thailand. There were no vaccine-related serious adverse events reported during the surveillance period. In conclusion, active pharmacovigilance confirms that the recombinant pertussis vaccines aP_gen (Pertagen) and TdaP_gen (Boostagen) are safe in adolescents and adults, including pregnant women vaccinated in the second or third trimester of pregnancy.

The burden of laboratory-confirmed pertussis in low- and middle-income countries since the inception of the Expanded Programme on Immunisation (EPI) in 1974: a systematic review and meta-analysis

BACKGROUND

An effective vaccine against Bordetella pertussis was introduced into the Expanded Programme on Immunisation (EPI) by WHO in 1974, leading to a substantial global reduction in pertussis morbidity and mortality. In low- and middle-income countries (LMICs), however, the epidemiology of pertussis remains largely unknown. This impacts negatively on pertussis control strategies in these countries. This study aimed to systematically and comprehensively review published literature on the burden of laboratory-confirmed pertussis in LMICs over the 45 years of EPI.

METHODS

Electronic databases were searched for relevant literature (1974 to December 2018) using common and MeSH terms for pertussis. Studies using PCR, culture or paired serology to confirm Bordetella pertussis and parapertussis in symptomatic individuals were included if they had clearly defined numerators and denominators to determine prevalence and mortality rates.

RESULTS

Eighty-two studies (49,167 participants) made the inclusion criteria. All six WHO regions were represented with most of the studies published after 2010 and involving mainly upper middle-income countries (n = 63; 77%). PCR was the main diagnostic test after the year 2000. The overall median point prevalence of PCR-confirmed Bordetella pertussis was 11% (interquartile range (IQR), 5-27%), while culture-confirmed was 3% (IQR 1-9%) and paired serology a median of 17% (IQR 3-23%) over the period. On average, culture underestimated prevalence by 85% (RR = 0.15, 95% CI, 0.10-0.22) compared to PCR in the same studies. Risk of pertussis increased with HIV exposure [RR, 1.4 (95% CI, 1.0-2.0)] and infection [RR, 2.4 (95% CI, 1.1-5.1)]. HIV infection and exposure were also related to higher pertussis incidences, higher rates of hospitalisation and pertussis-related deaths. Pertussis mortality and case fatality rates were 0.8% (95% CI, 0.4-1.4%) and 6.5% (95% CI, 4.0-9.5%), respectively. Most deaths occurred in infants less than 6 months of age.

CONCLUSIONS

Despite the widespread use of pertussis vaccines, the prevalence of pertussis remains high in LMIC over the last three decades. There is a need to increase access to PCR-based diagnostic confirmation in order to improve surveillance. Disease control measures in LMICs must take into account the persistent significant infant mortality and increased disease burden associated with HIV infection and exposure.

Seroprevalence of Bordetella pertussis antibodies and anti-pertussis antibody response after a single dose of reduced-antigen combined diphtheria, tetanus, and acellular pertussis vaccine (Tdap) in pregnant Thai women

BACKGROUND

Maternal immunization with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) has recently been implemented to prevent infant pertussis. Tdap is still not routinely recommended in Thailand, and there are limited data to support or challenge this strategy.

OBJECTIVES

The primary aim was to determine the seroprevalence of anti-pertussis toxin antibodies (anti-PT IgG) among pregnant Thai women. The secondary aims were to evaluate antibodies response after Tdap vaccination between seronegative and seropositive mothers and to compare the different antibody titers at delivery among seropositive mothers who received Tdap to those who received tetanus-diphtheria vaccine (Td).

METHODS

This randomized clinical trial was conducted during April 2018 to April 2019 at Siriraj Hospital, Bangkok, Thailand. A total of 129 pregnant women were included. Paired blood samples for anti-PT IgG levels were obtained during the first antenatal visit and at delivery. A baseline cut-off value of <5 IU/ml indicated seronegativity. There were 29 exclusions from the original 129 enrollment. All seronegative participants (n = 69) received Tdap, while the seropositive group were randomized 1:1 to receive either Tdap (n = 18) or Td (n = 13) during 27-36 weeks' gestation. The antibody levels from both sera were compared between groups.

RESULTS

The seroprevalence of maternal anti-PT IgG was 33.3% (43/129). There was no significant difference in the increment of antibody levels after Tdap vaccination between the seronegative and seropositive groups (30.2 vs. 42 IU/ml; p = 0.183). Among seropositive groups, all Tdap recipients had increased antibody titers at delivery, while all Td recipients showed waning of immunity throughout gestation. (42 IU/ml vs. -7.4 IU/ml; p < 0.001).

CONCLUSION

Most pregnant Thai women have seronegative against pertussis. Most seropositive mothers had initial low antibody titers and their immunity significantly decreased before delivery. Our findings highlight the need for universal pertussis immunization in pregnancy regardless of individual baseline immunity.

Seroprevalence of an antibody against diphtheria, tetanus, and pertussis among the elderly in Khon Kaen, Thailand

BACKGROUND

Owing to a declining birth rate and longer lifespan, the number of elderly people (≥ 60 years) in Thailand has grown rapidly. However, the elderly are at significant risk of infectious diseases because they have never been immunized, because they have not been completely immunized, or because their immunity has waned. Immunity against infectious diseases in the elderly is an important means of controlling diseases in the community. Our objective was to evaluate the seroprotective rate against diphtheria, tetanus, and pertussis in the elderly Thai population.

METHODS

In total, 430 healthy individuals from the northeastern region of Thailand were enrolled in this study and stratified into five age groups: 60-65, 66-70, 71-75, 76-80, and > 80 years. Serum samples were collected and quantitatively analyzed for diphtheria, tetanus, and pertussis IgG antibody by using commercial ELISA kits. For anti-diphtheria toxoid and anti-tetanus toxoid ELISA, values < 0.01 IU/ml were interpreted as seronegative, and for anti-Bordetella pertussis toxin ELISA, values < 5 IU/ml were interpreted as seronegative; these definitions were in accord with previous studies.

RESULTS

For diphtheria toxoid Ab, the majority of the population had antibody levels > 0.01 IU/ml. For tetanus anti-toxoid Ab, the majority of the population had antibody levels of > 0.01 IU/ml, of which approximately 34% had durable antibody protection levels (DAPL) of ≥ 1 IU/ml. Meanwhile, nearly 45% of the population had an Ab level against pertussis lower than the protectivity level.

CONCLUSIONS

In total, 97.2%, 83.5%, and 55.8% of the population had a higher antibody level than the minimal protective level for diphtheria, tetanus, and pertussis, respectively. In order to prevent an outbreak of these diseases in the future, the elderly should be administered with Tdap revaccination to provide diphtheria herd immunity in the population; this will increase cocoon phenomenon for pertussis and protect the population from tetanus-prone injury.

Pertussis detection in children with cough of any duration

Background

The diagnosis of pertussis in clinical practice continues to be a challenge worldwide as the symptoms are variable. We aimed to determine the prevalence of pertussis in Chinese children irrespective of cough duration and explore the clinical characteristics of children with pertussis with different cough durations.

Methods

This was a prospective study of children 1 month to 11 years of age with different cough durations in one large Chinese hospital. Bilateral deep posterior nasopharyngeal swabs and venepuncture for full blood count, CRP and serology and sputum were obtained when possible for investigation. E-test strips were used for testing the susceptibility of the B.pertussis isolates against erythromycin, azithromycin, sulphamethoxazole/trimethoprim, levofloxacin, amoxicillin and doxycycline. Demographic, clinical and laboratory information on culture and antimicrobial susceptibility testing was collected from children, and analyzed using SAS v.10 (SAS Institute Inc., USA).

Results

After exclusions we analyzed 312 children. Ninety-seven (31.1%) children had laboratory evidence of pertussis. When grouped by cough duration, few characteristics were significant between children with and without pertussis. Of the 36 isolates, 72.2% (26/36)could not be inhibited by erythromycin and azithromycin at all. The MIC50 and MIC90 to amoxicillin were 0.75 mg/L and 1 mg/L respectively, sensitive to amoxicillin by the EUCAST points.

Conclusions

The “one-size-fits-all” clinical pertussis case definition is no longer optimal to recognize this disease. A large comprehensive study of children with all types of cough is required to make substantial inroads into increasing both the sensitivity and specificity in pertussis diagnosis, which will have a beneficial impact on public health. Amoxicillin maybe an alternative for children with marolide-resistant B.pertussis infection; however, local sensitivities are required to inform clinical practice.

Increased susceptibility to pertussis in adults at childbearing age as determined by comparative seroprevalence study, China 2010-2016

OBJECTIVES

This study was aimed to determine pertussis specific serum PT-IgG antibodies in healthy individuals during 2010 and 2015/2016 in Beijing, China.

METHODS

A total of 3884 healthy individuals were included: 3058 aged 3-69 years randomly selected from an epidemiological survey conducted in 2010, and 826 aged 20-39 years selected from those who attended an annual medical examination in 2015/2016. Serum PT-IgG antibodies were determined using the Serion/Virion ELISA kits.

RESULTS

Of 3058 subjects in 2010, 167 (5.5%) and 39 (1.3%) subjects had PT-IgG antibodies ≥40 IU/ml and ≥100 IU/ml, respectively. No differences were observed among different age groups. Altogether, 26.2% had undetectable PT-IgG antibodies (<5 IU/ml), and the highest undetectable rate of 56.8% was found in children aged 3-5 years. When the age group of 20-39 years was compared between the two periods, no difference was found in seroprevalence of PT-IgG antibodies ≥ 40 IU/ml (5.1% vs. 4.0%). However, an undetectable rate of PT-IgG antibodies was significantly higher in 2015/2016 than that in 2010 (57.4% vs. 29.1%, p < 0.001).

CONCLUSIONS

Our results showed that about 5% of individuals had PT-IgG antibodies indicative of a recent infection, and adults at childbearing age have an increased risk to pertussis in China.

The burden of pertussis in older adults: what is the role of vaccination? A systematic literature review

INTRODUCTION

Pertussis (whooping cough) is a vaccine-preventable disease; however, neither natural- nor vaccine-induced protection is life-long. Although generally not severe in adults, pertussis can be associated with complications in patients with chronic conditions such as asthma or chronic obstructive pulmonary disease, and can be readily transmitted to more vulnerable populations, including neonates before they complete their primary vaccination. Furthermore, as the global population ages, the health and economic burden of the disease is expected to rise. Areas covered: A systematic literature review was conducted to ascertain the current epidemiological and financial burden of pertussis in older adults and to discuss the potential value of a booster vaccination in this population. Expert commentary: Our review indicates a considerable underestimation of the pertussis burden amongst older adults. Seroprevalence studies consistently demonstrate that the reported incidence may be much lower than the actual incidence. Tetanus toxoid-reduced diphtheria toxoid and acellular pertussis vaccines are immunogenic in older adults, induce high booster responses and are well-tolerated. There is therefore a good rationale for the advocacy of booster pertussis vaccination throughout life to prevent pertussis infection and its transmission, especially in adults aged ≥50 years.

Clinically Diagnosing Pertussis-associated Cough in Adults and Children: CHEST Guideline and Expert Panel Report

BACKGROUND

The decision to treat a suspected case of pertussis with antibiotics is usually based on a clinical diagnosis rather than waiting for laboratory confirmation. The current guideline focuses on making the clinical diagnosis of pertussis-associated cough in adults and children.

METHODS

The American College of Chest Physicians (CHEST) methodologic guidelines and the Grading of Recommendations, Assessment, Development, and Evaluation framework were used. The Expert Cough Panel based their recommendations on findings from a systematic review that was recently published on the topic; final grading was reached by consensus according to Delphi methodology. The systematic review was carried out to answer the Key Clinical Question: In patients presenting with cough, how can we most accurately diagnose from clinical features alone those who have pertussis-associated cough as opposed to other causes of cough?

RESULTS

In adults, after pre-specified meta-analysis exclusions, pooled estimates of sensitivity and specificity were generated for only 4 clinical features: paroxysmal cough, post-tussive vomiting, inspiratory whooping, and absence of fever. Both paroxysmal cough and absence of fever had high sensitivity (93.2% [95% CI, 83.2-97.4] and 81.8% [95% CI, 72.2-88.7], respectively) and low specificity (20.6% [95% CI, 14.7-28.1] and 18.8% [95% CI, 8.1-37.9]). Inspiratory whooping and posttussive vomiting had a low sensitivity (32.5% [95% CI, 24.5-41.6] and 29.8% [95% CI, 18.0-45.2]) but high specificity (77.7% [95% CI, 73.1-81.7] and 79.5% [95% CI, 69.4-86.9]). In children, after pre-specified meta-analysis exclusions, pooled estimates of sensitivity and specificity were generated for only 1 clinical feature in children (0-18 years): posttussive vomiting. Posttussive vomiting in children was only moderately sensitive (60.0% [95% CI, 40.3-77.0]) and specific (66.0% [95% CI, 52.5-77.3]).

CONCLUSIONS

In adults with acute (< 3 weeks) or subacute (3-8 weeks) cough, the presence of whooping or posttussive vomiting should rule in a possible diagnosis of pertussis, whereas the lack of a paroxysmal cough or the presence of fever should rule it out. In children with acute (< 4 weeks) cough, posttussive vomiting is suggestive of pertussis but is much less helpful as a clinical diagnostic test. Guideline suggestions are made based upon these findings and conclusions.

Clinical Characteristics of Pertussis-Associated Cough in Adults and Children: A Diagnostic Systematic Review and Meta-Analysis

BACKGROUND

Pertussis (whooping cough) is a highly infective cause of cough that causes significant morbidity and mortality. Existing case definitions include paroxysmal cough, whooping, and posttussive vomiting, but diagnosis can be difficult. We determined the diagnostic accuracy of clinical characteristics of pertussis-associated cough.

METHODS

We systematically searched CINAHL, Embase, Medline, and SCI-EXPANDED/CPCI-S up to June 2016. Eligible studies compared clinical characteristics in those positive and negative for Bordetella pertussis infection, confirmed by laboratory investigations. Two authors independently completed screening, data extraction, and quality and bias assessments. For each characteristic, RevMan was used to produce descriptive forest plots. The bivariate meta-analysis method was used to generate pooled estimates of sensitivity and specificity.

RESULTS

Of 1,969 identified papers, 53 were included. Forty-one clinical characteristics were assessed for diagnostic accuracy. In adult patients, paroxysmal cough and absence of fever have a high sensitivity (93.2% [CI, 83.2-97.4] and 81.8% [CI, 72.2-88.7], respectively) and low specificity (20.6% [CI, 14.7-28.1] and 18.8% [CI, 8.1-37.9]), whereas posttussive vomiting and whooping have low sensitivity (32.5% [CI, 24.5-41.6] and 29.8% [CI, 8.0-45.2]) and high specificity (77.7% [CI, 73.1-81.7] and 79.5% [CI, 69.4-86.9]). Posttussive vomiting in children is moderately sensitive (60.0% [CI, 40.3-77.0]) and specific (66.0% [CI, 52.5-77.3]).

CONCLUSIONS

In adult patients, the presence of whooping or posttussive vomiting should rule in a possible diagnosis of pertussis, whereas the lack of a paroxysmal cough or the presence of fever should rule it out. In children, posttussive vomiting is much less helpful as a clinical diagnostic test.

Immune persistence after pertussis vaccination

Pertussis is one of the most prevalent vaccine-preventable diseases worldwide. The true infection rate is significantly higher than the reported incidence rate. An increased prevalence of pertussis in older populations has been found, mainly caused by waning immunity after vaccination. Vaccine-induced immunity differs due to variation in vaccine content, schedule and coverage. Protection following acellular pertussis vaccines has been suggested to wane faster than whole cell pertussis vaccines. However, long-term immune persistence of whole cell pertussis vaccines may be confounded by a progressive acquisition of natural immunity. The World Health Organization has recommended that a switch from whole cell to acellular pertussis vaccines for primary immunization in infants should only be considered if additional periodic boosters or maternal immunization can be ensured and sustained in the national immunization schedules. In this review, we present data on immune persistence after different pertussis vaccinations and compare the findings from countries with different vaccination strategies. Future aspects in serological studies are briefly discussed.

Assessing the Evidence for Maternal Pertussis Immunization: A Report From the Bill & Melinda Gates Foundation Symposium on Pertussis Infant Disease Burden in Low- and Lower-Middle-Income Countries

Implementation of effective interventions has halved maternal and child mortality over the past 2 decades, but less progress has been made in reducing neonatal mortality. Almost 45% of under-5 global mortality now occurs in infants <1 month of age, with approximately 86% of neonatal deaths occurring in low- and lower-middle-income countries (LMICs). As an estimated 23% of neonatal deaths globally are due to infectious causes, maternal immunization (MI) is one intervention that may reduce mortality in the first few months of life, when direct protection often relies on passively transmitted maternal antibodies. Despite all countries including pertussis-containing vaccines in their routine childhood immunization schedules, supported through the Expanded Programme on Immunization, pertussis continues to circulate globally. Although based on limited robust epidemiologic data, current estimates derived from modeling implicate pertussis in 1% of under-5 mortality, with infants too young to be vaccinated at highest risk of death. Pertussis MI programs have proven effective in reducing infant pertussis mortality in high-income countries using tetanus-diphtheria-acellular pertussis (Tdap) vaccines in their maternal and infant programs; however, these vaccines are cost-prohibitive for routine use in LMICs. The reach of antenatal care programs to deliver maternal pertussis vaccines, particularly with respect to infants at greatest risk of pertussis, needs to be further evaluated. Recognizing that decisions on the potential impact of pertussis MI in LMICs need, as a first step, robust contemporary mortality data for early infant pertussis, a symposium of global key experts was held. The symposium reviewed current evidence and identified knowledge gaps with respect to the infant pertussis disease burden in LMICs, and discussed proposed strategies to assess the potential impact of pertussis MI.

[Recent progress in clinical research on pertussis]

Pertussis is a highly contagious respiratory disease. Despite the high vaccination coverage, re-emergence of pertussis has been reported in many countries over the past two decades. With the increase in the incidence of pertussis, there has been a shift in the epidemiological features: an increased incidence of pertussis has been noted in older children and adults, who normally lack typical clinical manifestations, and who may be easily missed according to current diagnostic references for pertussis. In order to achieve better prevention and treatment of pertussis, this review article summarized the recent research progress in the epidemiology, clinical features, etiology, diagnosis, treatment, and prevention of pertussis, particularly focusing on the diagnosis of pertussis in older children and adults.

[Recent progress in clinical research on pertussis]

Pertussis is a highly contagious respiratory disease. Despite the high vaccination coverage, re-emergence of pertussis has been reported in many countries over the past two decades. With the increase in the incidence of pertussis, there has been a shift in the epidemiological features: an increased incidence of pertussis has been noted in older children and adults, who normally lack typical clinical manifestations, and who may be easily missed according to current diagnostic references for pertussis. In order to achieve better prevention and treatment of pertussis, this review article summarized the recent research progress in the epidemiology, clinical features, etiology, diagnosis, treatment, and prevention of pertussis, particularly focusing on the diagnosis of pertussis in older children and adults.