Effectiveness of one and two doses of acellular pertussis vaccines against laboratory-confirmed pertussis requiring hospitalisation in infants: Results of the PERTINENT sentinel surveillance system in six EU/EEA countries, December 2015 - December 2019

BACKGROUND

Monitoring effectiveness of pertussis vaccines is necessary to adapt vaccination strategies. PERTINENT, Pertussis in Infants European Network, is an active sentinel surveillance system implemented in 35 hospitals across six EU/EEA countries. We aim to measure pertussis vaccines effectiveness (VE) by dose against hospitalisation in infants aged <1 year.

METHODS

From December 2015 to December 2019, participating hospitals recruited all infants with pertussis-like symptoms. Cases were vaccine-eligible infants testing positive for Bordetella pertussis by PCR or culture; controls were those testing negative to all Bordetella spp. For each vaccine dose, we defined an infant as vaccinated if she/he received the corresponding dose >14 days before symptoms. Unvaccinated were those who did not receive any dose. We calculated (one-stage model) pooled VE as 100*(1-odds ratio of vaccination) adjusted for country, onset date (in 3-month categories) and age-group (when sample allowed it).

RESULTS

Of 1,393 infants eligible for vaccination, we included 259 cases and 746 controls. Median age was 16 weeks for cases and 19 weeks for controls (p < 0.001). Median birth weight and gestational age were 3,235 g and week 39 for cases, 3,113 g and week 39 for controls. Among cases, 119 (46 %) were vaccinated: 74 with one dose, 37 two doses, 8 three doses. Among controls, 469 (63 %) were vaccinated: 233 with one dose, 206 two doses, 30 three doses. Adjusted VE after at least one dose was 59 % (95 %CI: 36-73). Adjusted VE was 48 % (95 %CI: 5-71) for dose one (416 eligible infants) and 76 % (95 %CI: 43-90) for dose two (258 eligible infants). Only 42 infants were eligible for the third dose.

CONCLUSIONS

Our results suggest moderate one-dose and two-dose VE in infants. Larger sample size would allow more precise estimates for dose one, two and three.

Vaccination against influenza in pregnant women in a maternity hospital in the Czech Republic in the season 2020-2021

OBJECTIVES

Pregnant women are among the priority groups to receive influenza vaccines in the Czech Republic since 2011, data on vaccination coverage are not yet available. The aim of the study was to determine the influenza vaccination coverage (IVC) and provide source data for further activities.

METHODS

A prospective observational study was performed in a large maternity hospital in Prague. The self-completed questionnaire was distributed to 5,475 pregnant women between September 1, 2020 and August 31, 2021. Questions included maternal sociodemographic characteristics, influenza vaccination status and sources of maternal vaccination recommendations during pregnancy.

RESULTS

A total of 4,617 completed questionnaires have been analysed. The median age of study participants (N = 4,592) was 33 years (range: 18-51 years). The majority (69.7%) of women had completed their university education, most women were childless (58.5%) or had one child (32.5%) before the start of the study. Less than 2% of women reported being vaccinated against influenza during their pregnancy (1.5%; 95% CI, 1.1-1.9%). Only 21% of women knew that it's possible to get vaccinated against influenza during pregnancy. Participants considered influenza vaccination in pregnancy as important (3.3%), useful (41.1%) and useless (44.4%). Out of 959 pregnant women who had information about influenza vaccination during pregnancy, only 6.9% were vaccinated, while among those who did not have this information, 0.1% were vaccinated during pregnancy (p < 0.001). The most frequent source of information was Internet, then media and a general practitioner.

CONCLUSIONS

The IVC during pregnancy in our study was extremely low. In order to improve IVC among pregnant women, it is necessary to increase awareness of recommendations and vaccination options among the public and professionals and incorporating vaccination recommendation in routine antenatal practice.

Peculiarities of Q fever and human cases reported so far in the Czech Republic

INTRODUCTION

Q fever is a zoonosis with a worldwide occurrence. Coxiella burnetii infection is most commonly transmitted by inhalation of air containing contaminated dust in cow, sheep and goat farming areas. The other modes of transmission are alimentary route (ingestion) and through sucking ticks. We set ourselves the goal of presenting a descriptive analysis of cases of Q fever in the Czech Republic (CZ) and former Czechoslovakia and draw attention to this often-overlooked issue.

METHODS

Summary of available information about Q fever was processed, and a narrative search of published cases of Q fever in the CZ and former Czechoslovakia, in Czech, Slovak and English, without time restrictions was performed. Furthermore, a descriptive analysis of Q fever cases reported to the Czech infectious diseases reporting system in 1982-2021 was done. After analysis, the available information system data were supplemented with data from a search of published scientific literature and weekly reports on the current epidemiological situation of the public health protection authorities of the CZ.

RESULTS

The disease has been reported in former Czechoslovakia and then in CZ since 1952. In 1952-1954, six outbreaks were reported with a total of 150 cases, mostly in connection with work with cattle. In 1980, a large-scale outbreak of Q fever affected 526 employees of the cotton production plant at Staré Město near Uherské Hradiště. Otherwise, units to dozens of cases were reported. From 1993 to 2021, 27 cases of the disease were detected in the CZ, of which 22 (81.5%) occurred in men. The age range was 0-60 years (mean 31, median 30 years). Seasonality by reporting month was highest in January and September.

CONCLUSION

There has been a decline in human cases of Q fever in the European Union (EU) in recent years, and only few cases of the disease occur in the CZ. Still, due to potential severity of the disease, the current climate change with the consequent increase in the spread of ticks as vectors of Coxiella, and animal movements associated with the global market, it is important to consider Q fever in the differential diagnosis. As part of the prevention, it is necessary to ensure compliance with basic hygiene rules, especially in at-risk occupations, and to consume only pasteurized dairy products. Vaccination of humans is not available in EU countries, although vaccination of livestock is possible.

What risk factors affect hospitalisation for confirmed pertussis cases among infants in the Czech Republic?

BACKGROUND

We estimated what risk factors affect hospitalisation for confirmed pertussis cases among infants (child up to 1 year) in the Czech Republic based on data from the questionnaire-based enhanced surveillance system (ESS) in years 2015, 2017 and 2019.

METHODS

Retrospective cohort study was conducted in which we assessed demographic, clinical data, vaccination status and risk/protective factors. Vaccination status was extracted from the electronic nationwide notification system (NNS). We performed descriptive, univariable and multivariable analysis using risk ratio (RR) and logistic regression with odds ratio (OR).

RESULTS

A total of 104 confirmed cases (27, 13, 64) were reported in the ESS during 2015, 2017 and 2019. Most cases were in age group 1 month (24), more males (57). Fifteen cases were vaccinated and 89 unvaccinated. Of 88 hospitalised cases, 31 cases reported stay in Intensive Care Unit (ICU). The median length of hospitalisation was 8 days. Although the variable vaccinated in infants was statistically significant in a univariable analysis for outcome hospitalisation, RR 0.76 (95% CI 0.53-1.10), it was not in multivariable. Hospitalisation was strongly associated with the younger age group of 0-3 months adjusted by a smoking family member in a household (OR = 9.72; 95% CI: 2.97-31.81). Stay in ICU was strongly correlated with the younger age group of 0-3 months (OR = 5.07; 95% CI: 1.44-17.87) and with a contact with confirmed or probable pertussis (OR = 7.05; 95% CI: 1.36-36.52).

CONCLUSIONS

Our study demonstrated younger age and contact with other pertussis case as risk factors for hospitalisation of infants with pertussis. It is necessary to consider adolescent and adult boosters, including vaccination during pregnancy. We suggest integrating the variables from the enhanced surveillance system into the nationwide notification system, in order to simplify the data reporting and evaluation. Further studies are needed to evaluate the ESS and to monitor the vaccination of pregnant women against pertussis.

Comparative Omics Analysis of Historic and Recent Isolates of Bordetella pertussis and Effects of Genome Rearrangements on Evolution

Despite high vaccination coverage, pertussis is increasing in many industrialized countries, including the Czech Republic. To better understand Bordetella pertussis resurgence, we analyzed historic strains and recent clinical isolates by using a comparative omics approach. Whole-genome sequencing showed that historic and recent isolates of B. pertussis have substantial variation in genome organization and form separate phylogenetic clusters. Subsequent RNA sequence analysis and liquid chromatography with mass tandem spectrometry analyses showed that these variations translated into discretely separated transcriptomic and proteomic profiles. When compared with historic strains, recent isolates showed increased expression of flagellar genes and genes involved in lipopolysaccharide biosynthesis and decreased expression of polysaccharide capsule genes. Compared with reference strain Tohama I, all strains had increased expression and production of the type III secretion system apparatus. We detected the potential link between observed effects and insertion sequence element–induced changes in gene context only for a few genes.

Incidence and severity of pertussis hospitalisations in infants aged less than 1 year in 37 hospitals of six EU/EEA countries, results of PERTINENT sentinel pilot surveillance system, December 2015 to December 2018

Introduction

PERTINENT is a pilot active surveillance system of infants hospitalised with pertussis in six European Union/European Economic Area countries (37 hospitals, seven sites).

Aim

This observational study aimed to estimate annual pertussis incidence per site from 2016 to 2018 and respective trends between 2017 and 2018. Pertussis cases were described, including their severity.

Methods

We developed a generic protocol and laboratory guidelines to harmonise practices across sites. Cases were hospitalised infants testing positive for Bordetella pertussis by PCR or culture. Sites collected demographic, clinical, laboratory data, vaccination status, and risk/protective factors. We estimated sites’ annual incidences by dividing case numbers by the catchment populations.

Results

From December 2015 to December 2018, we identified 469 cases (247 males; 53%). The median age, birthweight and gestational age were 2.5 months (range: 0–11.6; interquartile range (IQR): 2.5), 3,280 g (range: 700–4,925; IQR: 720) and 39 weeks (range: 25–42; IQR: 2), respectively. Thirty cases (6%) had atypical presentation either with cough or cyanosis only or with absence of pertussis-like symptoms. Of 330 cases with information, 83 (25%) were admitted to intensive care units including five deceased infants too young to be vaccinated. Incidence rate ratios between 2018 and 2017 were 1.43 in Czech Republic (p = 0.468), 0.25 in Catalonia (p = 0.002), 0.71 in France (p = 0.034), 0.14 in Ireland (p = 0.002), 0.63 in Italy (p = 0.053), 0.21 in Navarra (p = 0.148) and zero in Norway.

Conclusions

Incidence appeared to decrease between 2017 and 2018 in all but one site. Enhanced surveillance of hospitalised pertussis in Europe is essential to monitor pertussis epidemiology and disease burden.

Non-O1/non-O139 vibrios - occurrence not only in Europe in recent years

Non-O1/non-O139 vibrios refer to all vibrios except toxin producing Vibrio cholerae serogroups O1 and O139. The prevalence of illness caused by non-O1/non-O139 vibrios steadily increases all over the world in the last 20 years, which is very probably related to global warming. These infections are reported year-round from tropical and subtropical climate zones, but they were also detected in the mild climate zone of the United States of America and Europe. In mild climate, they have markedly seasonal occurrence, typically peaking in May to October. A human can be infected after ingestion of contaminated food, especially seafood and fish, or water or while bathing. In Europe, non-O1/non-O139 vibrios were detected in the Baltic Sea, North Sea and Mediterranean Sea but also in ponds and rivers. Depending on the pathogen entry route, the clinical manifestation may appear as gastroenteritis, otitis, wound infection or severe up to fatal illness, predominantly in immunocompromised patients. There is no specific prevention. Non-specific prevention includes good personal and food handling hygiene practices and avoiding contact of unhealed wounds with sea or surface swimming water. Given the severity and increasing frequency of infections caused by non-O1/non-O139 vibrios, they should be considered in differential diagnosis of gastrointestinal and wound infections, especially in patients with a history of consumption of fish and seafood or with a history of contact of unhealed wounds with sea or other open swimming water.

COVID-19 reinfections

Reports of SARS-CoV-2 reinfections are on the rise. This study focused on reinfections in patients with confirmed COVID-19 in the Czech Republic. Between 1 March 2020 and 9 November 2020, 362 084 cases with the onset of symptoms before 31 October 2020 were reported. Overall, 28 cases of symptomatic SARS-CoV-2 reinfections were identified, 11 in males and 17 in females, age range 25-80 years, median age 46 years. The interval between the first and second episodes of the disease ranged from 101 to 231 days, and the median interval was 201.5 days. During both symptomatic episodes, all patients have been tested by RT-PCR. Altogether 26 patients (92.9%) have been tested negative after recovery from the first episode of COVID-19. Symptomatic reinfections occurred in nearly 0.2% of all patients at risk. Most patients with reinfection had mild symptoms in both episodes, and only three episodes were moderate to severe. Thus, reinfections may have been underdiagnosed. In summary, COVID-19 reinfections are possible and not exceptional.

Susceptibility of clinical isolates of Bordetella pertussis to chemicals

THE AIM OF STUDY

To test clinical isolates of Bordetella pertussis from the National Reference Laboratory for Pertussis and Diphtheria for susceptibility to commonly available disinfectants. Another aim was to determine the concentration and exposure time for each chemical under real conditions of use and possibly to detect the emergence of resistance to disinfectants among 34 strains of B. pertussis referred to the National Reference Laboratory for Pertussis and Diphtheria in 2014 and 2015.

MATERIAL AND METHODS

A total of 34 clinical isolates of Bordetella pertussis were tested for susceptibility to chemical disinfectants by three different methods. The microsuspension method was used for the primary screening, and the tests were carried out without protein contamination. Further testing was conducted in accordance with standard EN 14885, where the test procedure consists of several steps. Step 1 involves quantitative suspension methods (Phase 2, Step 1), and step 2 uses methods designed for practice (Phase 2, Step 2). The quantitative suspension method modified according to EN 13727+A2 was used in step 1 to confirm bactericidal activity of the test products under the dirty conditions. In step 2, clinical isolates were tested using a quantitative carrier test method under the dirty conditions modified according to EN 14561. Based on this standard, the real conditions of product use are simulated. Four disinfectants differing in composition and intended use were tested.

RESULTS

Disinfectant No. 1 showed bactericidal activity at a concentration of 0.5% after 2 min of exposure in the case of immersion or at a concentration of 5% after 2 min of exposure when treated by wiping. Disinfectant No. 2 was active at a concentration of 0.1% after 2 min of exposure or at a concentration of 1% after 2 min of exposure, respectively. Disinfectant No. 3 did not show bactericidal activity even at a concentration of 100% after 5 min of exposure. Disinfectant No. 4 showed bactericidal activity at a concentration of 10% after 5 min of exposure or at a concentration of 30% after 2 min of exposure.

CONCLUSIONS

None of the strains tested was resistant. Using the methods that simulate the real conditions of use of disinfectants Nos. 1 and 2, it was possible to determine the concentration and exposure time needed to achieve disinfection of surfaces under the dirty conditions. Disinfectants Nos. 3 and 4 are not primarily intended for the treatment of surfaces but for the treatment of the skin and mucous membranes. The results obtained with the latter two products are interesting but inconclusive as the real conditions of their use were not simulated accurately. KEYWORDS Bordetella pertussis - susceptibility - disinfectants.

[Multiple-locus variable number tandem repeat analysis of Bordetella pertussis strains collected in the Czech Republic in 1967-2015: spread of a variant adapted to the population with a high vaccination coverage]

AIM

To perform multiple-locus variable number tandem repeat analysis (MLVA) of B. pertussis strains from the collection of the National Reference Laboratory for Diphtheria and Pertussis (NRL/DIPE), National Institute of Public Health (NIPH), Prague. The study strains were isolated from clinical specimens collected mostly in the Czech Republic over a nearly 50-year period from 1967 to 2015 (June). The isolates from three periods characterized by different vaccination strategies and trends in pertussis are compared for genetic diversity and distribution of MLVA types (MT). Based on the results obtained, the suitability for use of MLVA in the analysis of epidemic outbreaks of B. pertussis in the Czech Republic is considered.

MATERIAL AND METHODS

DNA samples extracted from B. pertussis strains included in the present study were examined by MLVA using the standard protocol. Data were processed by means of the eBURST algorithm and the calculation of the Simpson diversity index (DI) was used for the statistical analysis. Data were analyzed as a whole and also separately for strains from the three periods: 1967-1980, 1990-2007, and 2008-2015 (June).

RESULTS

Fourteen different MT were detected in the study strains, with three of them not being reported before. The most common MTs were MT27 and MT29. MT29 was predominant in 1967-1980 while MT27 was the most prevalent in 1990-2007 and 2008-2015 (June). The DI was the lowest (0.49) in 2008-2015 (June), and comparably higher DIs were calculated for the two previous periods (i.e. 0.667 for 1967-1980 and 0.654 for 1990-2007).

CONCLUSION

MLVA revealed a decrease in genetic diversity and shifts in MT distribution of B. pertussis strains isolated from clinical specimens in the Czech Republic from 1967 to 2015 (June). These shifts in the Czech Republic can be characterized as a progressive increase in global MTs at the expense of the locally unique ones. The most common MT, similarly to other geographical areas with long-term high vaccination coverage, is MT27. The results of MLVA of 136 B. pertussis strains can provide a background for using this method in molecular epidemiological analysis of smaller groups of strains.

[Antigenic variability of Bordetella pertussis strains isolated in 1967-2010 in the Czech Republic--possible explanation for the rise in cases of pertussis?]

OBJECTIVE

Comparison of antigenic structures of Bordetella pertussis (B. pertussis) strains isolated from 1967 to 2010 in the Czech Republic.

MATERIAL AND METHODS

Seventy strains of B. pertussis were referred to the National Reference Laboratory (NRL) for Pertussis and Diphtheria within the surveillance of pertussis from all over the Czech Republic (CR) between 1967 and 2010. To study the strains, the analysis was performed of the genome sequences encoding the surface immunogenic structures--the pertussis toxin S1 subunit gene (ptxA), pertactin gene region 1 (prnA), type 3 fimbriae gene (fim3)--and pertussis toxin promoter (ptxP) responsible for the regulation of the production of pertussis toxin.

RESULTS

For the study set of B. pertussis strains, the sequencing analysis revealed changes in all genomic regions studied. The isolates from three periods differ in the allelic profile. In period I (19671978) with the use of whole cell pertussis vaccine (wP), the following two profiles were the most common: ptxP(1), ptxA(2), prnA(1), fim3(1) and ptxP(1), ptxA(1), prnA(3), fim3(1). In period 2 (19902007) with the switch to acellular pertussis vaccine (aP), the most common profile was: ptxP(3), ptxA(1), prnA(2), fim3(2). Period 3 (20082010) with the use of aP was characterized by the predominance of the following two profiles which had never been found in period 1: ptxP(3), ptxA(1), prnA(2), fim3(2) and ptxP(3) ptxA(1), prnA(2), fim3(1).

CONCLUSIONS

Sequencing of the genomic regions ptxP, ptxA, prnA, and fim3 of B. pertussis strains isolated in the CR between 1967 and 2010 confirmed changes in the allelic variants of these regions. The incidence of strains carrying the new allelic variants was increasing after 1995 at the expense of those carrying the original variants. The study results can be interpreted as a partial genetic escape of pathogenic strains of B. pertussis beyond the reach of the pertussis vaccines.

Minimum inhibitory concentrations of erythromycin and other antibiotics for Czech strains of Bordetella pertussis

AIM OF THE STUDY

To test the susceptibility to first-line and alternative antibiotics of 70 Bordetella pertussis (B. pertussis) strains recovered from patients with whooping cough through national pertussis surveillance in the Czech Republic (CR) in 1967-2010.

MATERIAL AND METHODS

The minimum inhibitory concentrations (MICs) of erythromycin, clarithromycin, azithromycin, ciprofloxacin, and co-trimoxazole were tested by the reference agar dilution method on Bordet-Gengou agar with 15 % defibrinated sheep blood.

RESULTS

Each of the 70 study strains was inhibited by two concentrations of erythromycin and azithromycin (0.06 and 0.12 mg/l) and by three concentrations of clarithromycin (0.03, 0.06, and 0.12 mg/l), with the highest concentration of the MIC range being 0.12 mg/l for all these similar antibiotics. Tested in a 2-fold geometric dilution series, the concentration of erythromycin required to inhibit 90 % of the study strains (MIC90) was one dilution step lower (0.06 mg/l) than those of clarithromycin and azithromycin (0.12 mg/l). All study strains were inhibited by a single concentration of ciprofloxacin (0.06 mg/l) and two concentrations of co-trimoxazole (0.12 and 0.25 mg/l).

CONCLUSION

The panel of 70 Czech strains of B. pertussis appears to be homogeneous in terms of the MICs of the antibiotics tested, with two to three low concentrations being effective against all strains. To be inhibited, no strain required a higher concentration of erythromycin, clarithromycin, azithromycin, ciprofloxacin, or co-trimoxazole.

[Pertussis trend in children under one year of age in the Czech Republic in 1997-2013]

STUDY OBJECTIVE

To characterize the epidemiological situation of pertussis in children under one year of age in the Czech Republic in 1997-2013.

MATERIAL AND METHODS

The study cohort consisted of children under one year of age with laboratory confirmed pertussis reported to the communicable disease system from 1997 to 2013. A total of 265 pertussis cases were reported in children under one year of age over the study period. Selected demographic data, need for hospitalization, and vaccination history were evaluated in the study cohort.

RESULTS

Children under one year of age have shown a steady upward trend in reported cases of pertussis since the 1990s. The reported incidence of pertussis in this age group was the lowest in 1998 (1.1/100,000 population) and the highest in 2013 (31.3/100,000). In 1997-2013, 265 pertussis cases were reported in children under one year of age, 128 females and 137 males, to the communicable disease system in the Czech Republic. Most of these children, nearly 77%, developed pertussis within the first four months of life. Of the 265 children, 79% were not vaccinated before the onset of the disease and 21% were immunized with at least one dose of pertussis vaccine before developing the disease. As many as 75% of the children with pertussis needed hospitalization. Most of them, nearly 81%, were hospitalized with pertussis in the first four months of life and 90% of them in the first six months of life.

CONCLUSIONS

In 1997-2013, an upward trend was observed in pertussis cases in children under one year of age. Most children developed the disease within the first four months of life while not vaccinated against pertussis. This fact unambiguously supports the "cocoon" strategy, i.e. vaccination of the closest contacts of the child, and a booster dose at 25 years of age. At the same time, a question arises whether to provide vaccination to pregnant women.

A steady rise in incidence of pertussis since nineties in the Czech Republic

STUDY OBJECTIVE

The objective was to analyze the incidence and trends of pertussis in the Czech Republic, particularly by age groups. An important part of the analysis was the immunization coverage.

MATERIALS AND METHODS

The incidence data were obtained from the following information sources: archives of the National Institute of Public Health for the period up to 1964, archives of the Institute of Health Information and Statistics for 1965-1981, Communicable Disease Information System for 1982-1992 and Communicable Disease Notification System EPIDAT for 1992-2008. The mortality data were obtained, apart from the aforementioned sources, also from the literature. The case definition was based on that provided by the Bulletin of the Ministry of Health and the EC Directive. Cases were notified in accordance with the guidelines of the respective information systems and the principles of pertussis surveillance laid down by the regulations. An epidemiological investigation form was filled in for each case of pertussis, indicating the type of laboratory analysis. The methods used for laboratory diagnosis of pertussis were culture, serology and a PCR assay.

RESULTS

An upward trend in notified cases of pertussis has been observed since the 1990s. The highest annual number of cases (767) in the last 42 years was notified in 2008 (7.3/100,000 population). In 1988-2008, most (93.1%) cases were notified in patients aged 0-19 years. During this period the peak moved from the youngest and preschool age groups toward younger and older school age children (the highest age-specific incidence of pertussis, i.e., 79.8/100,000, was observed in 10-14-year-olds. In 2008, a 3.4 fold rise in pertussis cases was observed in 15-19-year-olds as compared with the rates in the last six years. More cases were also notified in the age groups of potential parents and grandparents. In the 0- year-old children, the incidence of pertussis was decreasing since the 1950s (3804.9/100,000 in 1956) to remain under 10.0/100,000 between 1974 and 1999. It showed a continuing upward trend from 3.8/100,000 in 1987 to 26.7/100,000 in 2008, even with three deaths notified, after 35 years, in 2005, 2007 and 2009.

CONCLUSION

Despite the high immunization coverage with pertussis vaccine (>97%), the pertussis incidence is rising in the Czech Republic. An upward trend in pertussis cases has been observed since 1993, peaking in 2008. More than 75 % of pertussis cases were notified in patients who had been vaccinated with 5 doses of pertussis vaccine before infection. During the period 1988-2008, the highest age-specific incidence, i.e., 79.8/100,000, was observed in 10-14-year-olds. After 35 years, three deaths from pertussis were notified in 2005, 2007 and 2009. All three fatal cases occurred in unvaccinated children under one year of age. The focus needs to be on active surveillance of pertussis and quality improvement of all its parts.

[Pertussis: a reemerging infection?]

STUDY OBJECTIVES

To analyze the incidence of pertussis in the Czech Republic, influencing factors and, in particular, the effect of vaccination on pertussis morbidity, clinical seriousness of the disease and circulation of Bordetella pertussis in the population. To study the causes of defective diagnosis and reporting and to propose remedial measures.

METHODS

Data on pertussis morbidity were obtained from the archives of the National Institute of Public Health and the public health information systems ISPO and EPIDAT. Mortality data were taken from the above sources and literature. The case definition was used as specified in the Methodical Guidance for Pertussis Surveillance and the EC Directive. Laboratory diagnosis was based on culture and serology. An at least fourfold increase in the serum antibody titer found within an experiment was considered as a positive result.

RESULTS

Pertussis together with diphteria and measles used to be among the most dangerous infections in childhood. The oldest mortality data date back to 1890 when 62 deaths per 100,000 population were reported. In 1951, the death rate still reached 3.6/100,000. The pertussis morbidity peaked in 1955 with 540 cases per 100,000 population. Vaccination against pertussis since the early 1950's led to a rapid reduction of morbidity in children. Nevertheless, higher pertussis morbidity rates were observed at 2-4-year intervals (in the so- called epidemic years). The lowest morbidity rates were reported during the 1980's. However, a stable upward trend has been observed over the following years. In 2006, a neonate died from pertussis. The age specific morbidity rates in 1980 through 2000 were highest in children under one year of age. This fact together with the regularly increased morbidity rates observed at 2-3-year intervals indicate that Bordetella pertussis still circulates in the population. While in the 1980's, the cases of pertussis were reported almost exclusively in children under one year of age, in the 1990's, they became more common also among children 1-4 years of age and started to be prevalent in children 10-14 years of age since 2001.

CONCLUSION

A high immunisation coverage (97%) with five doses of high quality whole-cell vaccine of Czech origin introduced into practice in 1958 played a crucial role in the reduction of pertussis morbidity from more than 500/100,000 in the mid-1950's to less than 0.5/100,000 in the 1980's. Nevertheless, this strategy did not lead to elimination of the causative agent in the population. It is evident that the current immunization scheme with the use of the available vaccines cannot solve the epidemiological situation. Since the efficacy of the currently available acellular pertussis vaccines is, at the best, the same as that of the whole-cell vaccines, any improvement of the current status cannot be expected. Only effective active surveillance, the use of new more immunogenic pertussis vaccines and revaccination of older age groups can result in desirable outcomes.