Intensity of the epidemic process of whooping cough under conditions of mass immunization over a period of many years

On the basis of analysis of whooping cough incidence in 1959 to 1975 in Moscow the authors present characteristics of the epidemic process under conditions of planned many-year immunization of children against this infection. Whooping cough morbidity proved to undergo significant changes-from sharp falls the first 8 years of immunization to a relative stabilization with a gradual reduction the last 5 years. Marked seasonal and periodic elevations persist against the background of reduction of morbidity. Preschool- and schoolchildren are equally involved in the epidemic process; the most frequently involved are nonvaccinated children aged 1 year and 4 to 10 years, which lost postvaccinal immunity. Further reduction of the severity of whooping cough and increase in the number of unimanifested forms of the infection was noted. This was apparently connected not only with immunization, but also with the reduction of the virulence of H. pertusis detected in studying the cultures isolated in Moscow from 1967 to 1974. The intensity indices of the epidemic process in whooping cough pointed to the necessity of using a more effective vaccine for the protection of children from whooping cough, despite the noted reduction of morbidity, and diminished severity of the course of the disease, and of the causative agent virulence.     

Whooping-cough vaccine. Statement by Joint Committee on Vaccination and Immunization of the Central Health Services Council and the Scottish Health Service Planning Council.

In 1974 it was recommended that pertussis vaccine should continue to be offered in a triple vaccine together with diphtheria and tetanus vaccines. Further data on the prevalence of whooping cough and the incidence of adverse reactions have shown no reason to change this policy; the hazard of whooping cough remains greater than that of immunization.     

Injury by hypertonic phosphate enema.

Over a 2-year period 67 strains of Bordetella pertussis were identified in 231 single specimens of nasopharyngeal secretions submitted from patients suspected to have whooping cough in the National Capital Region; 89.5% of the identifications were made by culture. Serotype 1,3 was predominant. At least 75% of the patients with bacteriologically confirmed whooping cough had not been fully immunized. There was no evidence that adenoviruses or other viruses played any important etiologic role in the 204 cases of whooping cough or whooping cough syndrome studied virologically.     

Study of intellectual performance of children in ordinary schools after certain serious complications of whooping cough. Swansea Research Unit of the Royal College of General Practitioners.

In a case-control study 27 index children from ordinary schools who had had convulsions or apnoea as a complication of whooping cough about eight years previously were compared with 27 children who had never had whooping cough and 15 who had had whooping cough without complications. Other factors likely to cause intellectual impairment after conception were considered. The index group had a significantly lower median intelligence quotient and poorer school attainment than either of the control groups. The results support the hypothesis that convulsions or apnoea as a complication of whooping cough may be associated with subsequent intellectual impairment.     

Growth retardation in weight and catch-up growth following infection by measles and whooping cough among babies of rural Zaire (Lake Tumba)

This study has shown that measles and whooping cough affect growth in weight among babies of rural Zaire (Lake Tumba). The average loss in weight due to measles, is more than twice the amount due to whooping cough. However, the time needed to regain the original growth channel after infection by measles, is about half the time needed to fully catch up after whooping cough. The amount of weight loss is proportional to the child's weight at the onset of the disease. There is no difference in the susceptibility to lose weight after measles or whooping cough, between boys and girls, nor between Oto and Twa. This study has also shown that the effect of measles and whooping cough on the growth in weight, is independent of the season of the hear, although the incidence of these diseases showed a significant seasonal pattern. Finally, this study gives evidence for the fact that the incidence of weight loss one month after the onset of measles or whooping cough is age-related.     

Whooping cough in adults.

During the 1970s whooping cough returned in Sweden after an absence of more than 10 years and is now seen in all age groups, During a three-year period 174 adults with culture-verified whooping cough were identified in Gothenburg. Most of the patients had typical symptoms with whooping attacks and often vomiting. The disease was long lasting but complications were rare. Physicians should be aware that whooping cough may occur in adults, since adults may be an important source of infection for infants and erythromycin given in the catarrhal phase may modify the clinical course.     

Etiology, clinical manifestations, and epidemiology in community-acquired respiratory infection in children in the Khabarovsk region

Clinico-epidemiological analysis and etiological verification of the outbreak of respiratory infection among school children in a rural district of the Khabarovsk territory, registered in spring 1997, were made. According to clinical signs, one-third of the patients had whooping cough, while the rest of the children exhibited the signs of respiratory infection with the symptoms of longering bronchitis. A half of the children had not been vaccinated against whooping cough, as they had been given injections of adsorbed DT vaccine with reduced antigen content. Etiologically, the diagnosis of whooping cough was confirmed in 57% of the patients with 47.4% of them having Bordetella pertussis monoinfection and 52.6% having mixed infection, mainly in combination with chlamydiosis. Whooping cough took an abnormal course under these circumstances. Treatment with erythromycin produced a good effect.     

Natural course of 500 consecutive cases of whooping cough: a general practice population study.

OBJECTIVE--To describe the natural course of whooping cough. DESIGN--Observational study of a general practice population. SETTING--Discrete semirural East Midlands practice of 11,500 patients. SUBJECTS--500 consecutive cases of whooping cough diagnosed clinically during 1977-92. MAIN OUTCOME MEASURES--Incidence of vomiting, whooping, apnoea, admission to hospital, and complications; duration and frequency of paroxysms. Pattern of spread. RESULTS--The incidence in the practice population was 4347/100,000 population compared with a notification rate for England and Wales of 717/100,000. Most cases were relatively mild. 284 patients vomited after paroxysms, 242 whooped, and 57 had apnoea. Duration and frequency of paroxysms varied widely. Female and unimmunised patients suffered more severe disease. Bordetella was isolated from fewer immunised patients (24/96 v 63/122 unimmunised). Infection was usually spread through contacts with someone with clinical whooping cough. Five patients developed pneumonia, three of whom had been immunised. Three patients required hospital admission. CONCLUSIONS--Most cases of whooping cough are relatively mild. Such cases are difficult to diagnose without a high index of suspicion because doctors are unlikely to hear the characteristic cough, which may be the only symptom. Parents can be reassured that a serious outcome is unlikely. Adults also get whooping cough, especially from their children, and get the same symptoms as children. The difficulty of early diagnosis and probability of missed cases reinforces the need to keep the incidence low through immunisation in order to protect infants, who are the most vulnerable.     

Surface-exposed antibody-accessible outer membrane proteins of Bordetella pertussis

The convalescent sera from a patient recovered from whooping cough were used to identify the surface-exposed antibody-accessible outer membrane proteins (OMPs) of Bordetella pertussis. The results indicated that the 69,000 OMP, the 40,000 porin, agglutinogens 2 and 3, and a number of presently unknown OMPs were exposed on the surface. The importance of these surface-exposed antigens in the protection against whooping cough is discussed.     

Duration of effectiveness of pertussis vaccine: evidence from a 10 year community study

A 10 year study of whooping cough in a discrete general practice community was performed to assess longitudinally the efficacy of pertussis vaccine from one to seven years after immunisation. Of the 436 cases of whooping cough over 10 years, 326 occurred in children aged 1-7 years. The rate of immunisation was known for each cohort of children born during each year, and the attack rate of whooping cough was thus calculated for those immunised and unimmunised. The attack rates were highest in those cohorts exposed to the epidemics of 1977-9, 1981-3, and 1985-7. The efficacy of the vaccine was calculated as a percentage as (attack rate in unimmunised group—attack rate in immunised group) × 100/attack rate in unimmunised group. It fell from 100% in the first year to 46% in the seventh, being 84% in the fourth and only 52% in the fifth.Thus the pertussis vaccine or its schedule of use does not seem to provide sufficient herd immunity to prevent outbreaks of whooping cough. Matters might be improved if vaccination against pertussis were included in the preschool immunisation programme.     

Inhibiting effect of ADP-ribosylation by pertussis toxin on passive transport of Ca2+ into the cell membrane of porcine myometrium]

ADP-ribosylation by whooping cough toxin of protein components of inside-out oriented vesicles of pig myometrium plasma membranes under conditions of their depolarization results in significant inhibition of passive transport of Ca2+ ions. The inhibiting effect is dose- and time-dependent. rho-Chloromercuribenzoate (0.5 mM) blocks the effect of whooping cough toxin, no such effect on Ca2+ transport being observed in control preparations.     

Attack rates of notified whooping cough in immunised and unimmunised children.

The incidence of whooping cough among immunised children under the age of six and among children of the same age who were not fully immunised was ascertained by analysing whooping-cough notifications from several health authorities. In the first three years of the study the results showed that attack rates were much higher in children who were not fully immunised than in those who were. This finding suggests that current vaccines provide young children with substantial protection against whooping cough.     

Interpretation of the contraindications to whooping cough vaccination.

The official recommendations on the contraindications to whooping cough immunisation are currently couched in general terms. The results of a simple inquiry made to directors of public health laboratories, general paediatriciains, paediatric neurologists, medical officers, general practitioners, and health visitors to see how they would interpret the contraindications in certain specific cases suggest that there is considerable uncertainty on how the contraindications should be interpreted. This is probably one factor responsible for the fall in the rate of whooping cough immunisation in the United Kingdom.     

Effect of vaccination on severity and dissemination of whooping cough.

A study was undertaken in general practice to clarify those factors, especially vaccinations, that influence the clinical picture and infectivity of whooping cough in the community. Although the range of the disease encountered was fairly mild, its duration was notable (mean +/- SD 50.9 +/- 32.1 days). By using multiway contingency table analysis it was found that in the more severe cases of whooping cough vaccination significantly shortened the illness (p less than 0.005) and reduced the number of coughing spasms (p less than 0.025). The protective effect of the vaccine was most notable in modifying infectivity within the family: 19% of vaccinated family contacts of index patients in whom the disease had been confirmed bacteriologically developed the disease when exposed to it compared with 72% of non-vaccinated contacts (p less than 0.001). These results show that whooping cough vaccination modifies the clinical illness and offers a worthwhile degree of protection to children exposed to the disease.     

Whooping cough after stopping pertussis immunisation.

An epidemic of whooping cough occurred in a rural practice in Shetland, containing 144 children under 16. Before July 1974 all children were immunised against pertussis, but after that date immunisation was stopped. Of the 134 children studied, 93 had been immunised. Sixty-five of the children developed whooping cough. The incidence of infection was similar in those who had and had not been immunised. The incidence was also similar in those born before and after July 1974. There was no evidence to support the routine use of pertussis immunisation in rural Shetland.     

Severity of notified whooping cough.

An analysis was made of the severity of over 8000 cases of whooping cough notified from October 1974 to March 1975. Ten per cent of these patients were admitted to hospital and there were 10 deaths. Severity was directly related to age, the disease being most severe in children under 1 year, especially those under 6 months. There was some evidence that previous vaccination reduced the severity of the disease, but the vaccination programme does not cover very young children, and for them whooping cough is a dangerous disease.     

Pathogenic properties of freshly isolated strains of the pertussis microbe

The serovar composition, toxicity, virulence and lymphocytosis stimulating activity (LSA) of B. pertussis strains circulating in the 1980-ies were studied in comparison with the strains circulating in previous years. The study revealed changes in the toxic properties of B. pertussis: their decrease in the years of the intensive immunization of children against whooping cough and rise at the period when the number of immunized children was reduced. The toxic properties and LSA in most B. pertussis strains were less pronounced in the 1980-ies than in the 1960-ies. The serovar composition of the circulating strains remained stable for 15 years with the prevalence of serovar 1.0.3.     

Protective effects of in vivo‐expressed autotransporters against Bordetella pertussis infection

Bordetella pertussis causes whooping cough, a severe and prolonged respiratory disease that results inhas high morbidity and mortality rates, particularly in developing countries. The number incidence of whooping cough cases is increasing in many countries despite high vaccine coverage. Causes for the re‐emergence of the disease include the limited duration of protection conferred by the acellular pertussis vaccines (aP)s and pathogenic adaptations that involve antigenic divergence from vaccine strains. Therefore, current vaccines therefore need to be improved. In the present study, we focused on five autotransporters: namely SphB1, BatB, SphB2, Phg, and Vag8, which were previously found to be expressed by B. bronchiseptica during the course of infection in rats and examined their protective efficiencies as vaccine antigens. The passenger domains of these proteins were produced in recombinant forms and used as antigens. An intranasal murine challenge assay showed that immunization with a mixture of SphB1 and Vag8 (SV) significantly reduced bacterial load in the lower respiratory tract and a combination of aP and SV acts synergistically in effects of conferring protection against B. pertussis infection, implying that these antigens have potential as components to for improvinge th the currently available acellular pertussis vaccine.

     

The interplay between determinism and stochasticity in childhood diseases

An important issue in the history of ecology has been the study of the relative importance of deterministic forces and processes noise in shaping the dynamics of ecological populations. We address this question by exploring the temporal dynamics of two childhood infections, measles and whooping cough, in England and Wales. We demonstrate that epidemics of whooping cough are strongly influenced by stochasticity; fully deterministic approaches cannot achieve even a qualitative fit to the observed data. In contrast, measles dynamics are extremely well explained by a deterministic model. These differences are shown to be caused by their contrasting responses to dynamical noise due to different infectious periods.     

Vaccines and exposed occupations

The use of safe and efficacious vaccines in occupational settings to protect workers from diseases to which they may be exposed is obvious and has been included in the employment law. Healthcare workers are particular exposed. Immunization has two purposes : protect the worker from contracting a disease, but also prevent him from disseminating the disease to weakened patients. It is important not only to take into account existing recommendations for immunization, but also to envisage their extension to teachers and staff of nurseries and primary schools. Routine vaccination against whooping cough, varicella, measles and hepatitis A is particularly warranted in these categories. Recommendations should also extend to medical students who are too often poorly protected and insufficiently warned against potential occupational exposure to pathogens and dissemination to their patients.