La coqueluche en pratique en 2006

Universal vaccination of infants against pertussis has transformed the epidemiology of the disease. Pertussis has however become frequent, although not often diagnosed, in adolescents and adults and thus contributes to permanent transmission of Bordetella pertussis in France and contamination of young infants at risk of severe disease. Control of transmission of pertussis in France necessitates reinforcement of vaccination with late boosters in adolescents and adults and, in addition, education of physicians to recognize and treat early cases of pertussis, especially in adolescents and adults with a persistant or chronic cough, and to take appropriate prophylactic measures (antibiotics and recall vaccination) of those in contact with confirmed cases. Effective treatment does little to reduce symptoms but it does reduce transmission. Macrolides are the recommended treatment for pertussis.     

Pertussis of adults and infants

Bordetella pertussis continues to circulate even in populations where a high vaccine coverage of infants and children is achieved. Cases in adolescents and adults are reported with increasing frequency in many countries. Adults are a reservoir for infections in very young infants, in whom pertussis may be severe and life-threatening. The salient clinical feature of pertussis in adolescents and adults is prolonged coughing, and recognising that pertussis does occur in these age groups is the most important step in its diagnosis. A laboratory diagnosis can be made by bordetella-PCR from nasopharyngeal swabs or secretions and by detection of antibodies, mainly to pertussis toxin; laboratory diagnosis is, however, not well standardised. Vaccination of adolescents and adults is now possible with acellular pertussis vaccines, which are well tolerated, immunogenic, and effective. Adolescent boosters and the vaccination of health-care workers are already included in vaccination calendars in some countries. Vaccine-recommending bodies and national health-care organisations must have locally relevant information on the transmission of pertussis from adults to infants to be able to make decisions on the advisability, feasibility, and priority for booster immunisation against pertussis.     

Pertussis – eine impfpräventable Erkrankung

Pertussis (whooping cough) is caused by Bordetella pertussis and B. parapertussis. It is a purely respiratory infection, which can be highly contagious. In countries with vaccination programs, the main targets are young infants, older non-vaccinated children, adolescents and adults. The disease remains endemic and cyclical worldwide, even in countries with a sustained high vaccination coverage. Pertussis is a notifiable disease in Germany but epidemiological data might not reflect the true burden of the disease. The main symptom is coughing for prolonged periods, which can be paroxysmal. The disease can take a severe course in infants with a possible fatal outcome but adults can also have a high rate of complications. Pertussis can be diagnosed by detecting Bordetella DNA by PCR or by detection of IgG antibodies to pertussis toxin. Antibiotics, such as macrolides can stop transmission but might not relieve the symptoms. Infant vaccination, which in Germany is carried out with four doses of combination vaccines with acellular pertussis components, can prevent the majority of cases. As immunity after infection and vaccination is not permanent, additional strategies comprising school entry boosters and the vaccination of adolescents and adults, as well as vaccinating special risk groups, such as pregnant women are recommended.     

Recent developments in pertussis

Pertussis causes nearly 300,000 deaths in children every year. Most deaths take place in developing countries, but the infection remains a priority everywhere. Pertussis vaccination protects infants and children against death and admission to hospital, but breakthrough disease in vaccinated people can happen. In high-mortality countries, the challenge is to improve timeliness and coverage of childhood vaccination and surveillance. In regions with low mortality and highest coverage, pertussis is frequently the least well-controlled disease in childhood vaccination programmes. Some countries have reported a rise in pertussis in adolescents, adults, and pre-vaccination infants, but how much these changes are real or a result of improved recognition and surveillance remains uncertain. In response, several countries have introduced adolescent and adult acellular pertussis vaccine boosters. The effect so far is unknown; assessment is impeded by poor data. Uncertainties still persist about key variables needed to model and design vaccination programmes, such as risk of transmission from adults and adolescents to infants. New vaccination strategies under investigation include vaccination of neonates, family members, and pregnant women.     

Progress in the diagnosis,prevention, and treatment of pertussis

Pertussis (“whooping cough”), caused by the gramnegative pleomorphic bacillus Bordetella pertussis, is a highly contagious, potentially life-threatening respiratory tract illness that has re-emerged worldwide as a cause of substantial morbidity and mortality in infants, children, and adolescents, even in countries with high vaccination rates. Waning immunity after immunization during childhood has been associated with a growing pool of susceptible adolescents and adults who are capable of transmitting pertussis to vulnerable unvaccinated or incompletely vaccinated infants. The use of acellular pertussis vaccine boosters in adolescents has been proposed and is likely to be recommended. Active immunization and improved methods for early diagnosis are key in the management of pertussis, and represent the most rapidly evolving aspects of this disease.     

Tos ferina en España. Situación epidemiológica y estrategias de prevención y control. Recomendaciones del Grupo de Trabajo de Tos ferina

A large increase of pertussis incidence has been observed in recent years in countries with high vaccination coverage. Outbreaks of pertussis are increasingly being reported. The age presentation has a bipolar distribution: infants younger 6 months that have not initiated or completed a vaccination schedule, and adolescents and adults, due to the lost of natural or vaccine immunity over time. These epidemiological changes justify the need to adopt new vaccination strategies in order to protect young infants and to reduce pertussis incidence in all age groups.     

The case for maternal vaccination against pertussis

Despite high vaccine coverage, the incidence of pertussis is increasing in a number of countries. Particularly alarming is the increase of pertussis in infants too young to be (fully) vaccinated, because the highest morbidity and mortality is observed in this category. Maternal vaccination offers the possibility to protect infants from birth until immunity is induced by active vaccination, and has been shown to be effective and safe for tetanus over long periods of time. Maternal vaccination studies with whole-cell pertussis vaccines have not shown serious adverse effects in mother and child. In one study, protection of newborn babies was found. Additional support for the efficacy of maternal vaccination comes from studies showing that transfer of antibodies confers protection against pertussis. Maternal vaccination might be an effective way to decrease morbidity and mortality caused by pertussis in newborn babies.     

Conduite à tenir devant un ou plusieurs cas de coqueluche

The evolution of the epidemiology of pertussis, new licensed macrolides and vaccines, new recommendations for vaccination among adolescents and adults need an update of the French guidelines for prevention of the disease around one or grouped cases of the disease. A particular attention should be raised to the diagnosis of whooping cough in adults who are presently the main reservoir of Bordetella pertussis. Whooping cough in adults presents as an unexplained prolonged cough with nocturnal exacerbation witch accounts for most of the contaminations of young infants. A bacteriological confirmation of pertussis should be provided before implementation of preventive measures: culture and PCR are presently the gold standard for the diagnosis of pertussis in infants, children and even adults who have been coughing for less than 20 days. Later on, serology (Elisa, immuno-empreinte) is the only technique available, but cannot be interpreted if the patient has been vaccinated less than one year ago. Infants under three months should be admitted to hospital and every case submitted to respiratory isolation. Eviction from the community should be pronounced within the five first days following the onset of an effective antibiotic treatment. New macrolides should be favoured: clarithromycine for seven days or azithromycine for five days. Household contacts should be given the same prophylactic antibiotic treatment: children and adolescent not correctly immunized, parents of the index case as adults parents of not or not completely immunized infants. The vaccination program of the household should be updated. The same measures should be applied in case of grouped cases (at least two contemporary or consecutive cases in the same area). In that case, the Public Health System doctors should be involved in the investigation and the classification of the cases. The close contacts not or not completely immunized should be prescribed and antibiotic prophylaxis and an update of their vaccination program. Among the occasional contacts, high-risk people only should be treated. In the day care centres an antibioprophylaxis should be given to children who have received less than four vaccine shots against pertussis and to the personnel contact to the cases as well. In the schools, the antibiotic prophylaxis should be prescribed to all children of the classroom(s) not completely vaccinated and to the teacher(s) as well. In the boarding schools and institutions with handicapped children, antibiotic prophylaxis could be applied to every member if the pertussis vaccine coverage is at less than 50%. In hospitals, coughing personnel should wear masks and investigations towards pertussis should be performed in people with a more than seven day unexplained cough. Preventive measures should be applied in case of confirmation of pertussis.     

Prospects for prevention of childhood infections by maternal immunization

PURPOSE OF REVIEW: To review the literature on using maternal immunization as a strategy to prevent infections in young infants aged below 6 months RECENT FINDINGS: Maternal immunization continues to reduce the incidence of neonatal tetanus worldwide. Despite increased influenza-related morbidity and mortality in pregnant women and in infants aged less than 6 months, compliance with US recommendations for immunization against influenza in pregnancy is poor. Polysaccharide vaccines against Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis are safe and immunogenic in pregnancy. Protein conjugate vaccines against these infections would be likely to induce higher maternal antibody levels and improve placental transport, thereby further reducing the maternal and infant disease burden. Further studies of acellular pertussis vaccines for use in adolescents and adults should evaluate if maternal immunization could prevent life-threatening pertussis in young infants. Maternal immunization against group B streptococcus is projected to be superior to screening and/or chemoprophylaxis strategies in decreasing infant disease. SUMMARY: Maternal immunization, with the passage of protective antibody to infants, is a potential strategy to prevent infection in infants who have not completed their primary immunization series from both specific infections of infancy and vaccine-preventable illnesses. Further evaluation of this strategy is supported by medical literature, but liability and educational barriers exist.     

Adults are whooping, but are internists listening?

Although studies have shown that pertussis is responsible for approximately 20% to 30% of cases of cough lasting more than 2 weeks in adults and adolescents, physicians have generally considered pertussis a disease that affects only children. Epidemiologic trends demonstrate that the incidence of pertussis has been rising, especially in adolescents and adults. Consequently, pertussis is not a "zebra" diagnosis but deserves a place among the community-acquired list of adult pathogens. Increased awareness among physicians about pertussis is important because adults may transmit the infection to infants, in whom the disease often leads to hospitalization and may result in death. Reporting this disease to the local health department is critical to its control because both case-patients and their close contacts should receive antimicrobial prophylaxis. A booster vaccine for adolescents and adults is likely to become available in the near future, so this is an important time to ensure that all physicians, not just pediatricians, are knowledgeable about the diagnosis, treatment, and reporting requirements for pertussis.     

Whooping cough: the current scene

Pertussis, a highly contagious disease caused by Bordetella pertussis, is making a comeback globally despite good immunization coverage. The developed countries have also shown a shift in the epidemiology of the disease to the adolescent and the adult age group, leading to a revision of their vaccination policies. The disease epidemiology in the South East Asian region seems poised for a similar change. Outbreaks have been reported among children and adults in countries such as Afghanistan, Israel, and Taipei. The anticipation and early recognition of this change in the epidemiology is important because the affected adolescents and adults act as reservoirs of the disease to the vulnerable population of infants, for whom the disease can be life threatening. The clinical presentation can be atypical in the adolescent age group, and the disease is often misdiagnosed. With the availability of polymerase chain reaction and serology, the disease can be diagnosed even later in the course of the disease when culture results are often negative. The whole-cell pertussis vaccine dramatically reduced the incidence of the disease but fell into disrepute due to the rare serious neurologic side effects that led to the introduction of the acellular pertussis vaccine, which led to fewer adverse reactions and also proved to be safe and effective in the adolescent age group when used as a booster. However, the cost of the acellular vaccine is may be prohibitive for widespread use in the developing nations of the South East Asian region.     

Consensus on the clinical and microbiologic diagnosis of Bordetella pertussis, and infection prevention. Expert Group on Pertussis Vaccination

Pertussis continues to be responsible for a significant disease burden worldwide. Although immunization practices have reduced the occurrence of the disease among children, waning vaccine- and infection-induced immunity still allows the disease to affect adolescents and adults who, in turn, can transmit the disease to non-immunized or partially immunized infants. This document is the result of a meeting in Mexico City of international experts who analyzed recent medical information in order to establish the current status of the epidemiology, diagnosis and surveillance of pertussis and, especially, the value of the dTpa booster dose in adolescents and adults as a pertussis prevention strategy in Mexico.     

Hepatitis B vaccines

Immunization is the most effective way to prevent transmission of HBV and, hence, the development of acute or chronic hepatitis B. The national strategy to eliminate transmission of the virus in the United States includes vaccination of all newborn infants, children, adolescents, and high-risk adults. Postexposure prophylaxis is also advocated, depending on the vaccination and anti-HBs status of the exposed person. Seroprotection after vaccination, defined as anti-HBs > or = 10 mIU/mL, is achieved in over 95% of all vaccinees. The hepatitis B vaccines are very well tolerated with usually minimal adverse effects. Predictors of non-response include increasing age, male gender, obesity, tobacco smoking, and immunocompromising chronic disease. For those who remain nonresponders after the second series of vaccination, adjuvants such as GM-CSF may be considered, but their results are variable.     

Pertussis-induced cough

Pertussis (whooping cough) is one of the commonest vaccine preventable diseases in the UK, despite vaccination coverage being maintained for the last 15 years at over 90% among infants and the addition of a pre-school booster to the UK national immunisation programme in 2001. However, it is known that pertussis vaccine does not confer long-term immunity to clinical infection. Evidence of pertussis infection has been reported in 37% of children presenting in UK primary care and 20% of adolescents and adults presenting in Canadian health centres with persistent cough. In children and adults with persistent cough, paroxysmal coughing is the most sensitive indicator of pertussis, but has poor specificity and limited diagnostic value. Vomiting and whooping, particularly in combination, are stronger predictors of pertussis. Cough duration is longer in children than in adults with pertussis (median cough duration 112 days versus 42 days); individuals may take even longer to recover fully and regain previous levels of exercise tolerance. A diagnosis of pertussis may be confirmed by culture, Polymerase Chain Reaction (PCR) or serology. Single estimates of anti-pertussis toxin (PT) antibody titres in blood or oral fluid samples are highly specific. There are currently no proven efficacious treatments for pertussis-induced cough. Treatment with macrolide antibiotics reduces the duration of an individual's infectious period, but does not alter the duration of cough. Further research is needed to re-examine the epidemiology of pertussis in countries with different vaccination schedules, find efficacious treatments and develop methods of measuring cough frequency and severity in patients with pertussis-induced cough.     

Diphtheria in Latvia, 1986-1996

After nearly two decades without a diphtheria case in Latvia, the disease reappeared in 1986. From 1990 to 1996, case counts were highest among adults 40-49 years of age, school-aged children, and adolescents. Nonetheless, the average annualized incidence of disease was highest among infants and preschoolers. In August 1995, mass vaccination efforts began to provide adults 25-60 years of age with at least one dose of vaccine. By the end of the year, a 77% coverage rate was achieved, resulting in a decrease of reported diphtheria cases by 1996. From February to September 1997, special outreach efforts were focused on hard-to-reach populations; as a result, by June 1997, 55% of adults had received three doses of vaccine. While decreases in the incidence of and morbidity from diphtheria have occurred, additional efforts still need to be concentrated on improving vaccination coverage in adults and children <2 years of age and in reducing mortality from diphtheria.     

Epidemiology and prevention of hepatitis B

The primary goal of hepatitis B prevention programs is reduction of chronic hepatitis B virus (HBV) infection and HBV-related chronic liver disease. Although donor screening, risk-reduction counseling and services, and effective infection control practices can reduce or eliminate the potential risk for HBV transmission, immunization is by far the single most effective prevention measure. Worldwide, the integration of hepatitis B vaccine into existing childhood vaccination schedules has the greatest likelihood of long-term success. However, by 2000, only 116 of 215 countries had such a policy, representing 31% of the global birth cohort. In addition, efforts must be strengthened to vaccinate older adolescents and adults with high-risk behaviors or occupations in countries where most HBV transmission and the morbidity associated with acute hepatitis B occur among persons in these age groups. Although continued immunization of successive birth cohorts should achieve the eventual elimination of HBV transmission, this will not occur for decades without successful vaccination of adults at increased risk for infection.     

Current status and vaccine indication for hepatitis A virus infection in Korea

One of the major cause of recent acute viral hepatitis in Korean adults is hepatitis A virus (HAV) infection. Most of hepatitis A cases are young adults in their twenties or thirties, and the severity of the disease is related to the age of patients. The seroprevalence of HAV among the adolescents and young adults in their teens and twenties is about 10%, which suggests that a growing number of young adults are susceptible to HAV infection. Development of more adult cases with severe presentation is expected in the near future, and some preliminary data suggest the incidence rate of hepatitis A in Korea might be higher than 20/100,000 population. This clinical features and the epidemiological shift of HAV urge to promote childhood vaccination and consider catch-up vaccination for adolescents and young adults. More extensive evaluation on the nationwide epidemiology of HAV infection, cost-benefit analysis of HAV vaccination, and setting-up of guidelines for HAV vaccination are urgently warranted.     

Mass vaccination of children with pertussis toxoid--decreased incidence in both vaccinated and nonvaccinated persons.

During 1979-1995, there was no vaccination against pertussis in Sweden. With the aim of studying the epidemiology and transmission of pertussis, mass vaccination with pertussis toxoid of children born during the 1990s was instituted in the G?teborg area (population, 778,597) in 1995. Infants were offered 3 doses of pertussis toxoid combined with diphtheria and tetanus toxoids. Children aged > or =1 year were offered 3 doses of pertussis toxoid alone. From June 1995 through February 1999, 167,810 doses of pertussis toxoid were given to 61,219 children born during the 1990s (56% received 3 doses). The number of Bordetella pertussis isolates per year declined from 1214 (1993-1995) to 64 (January 1997 through June 1999; P<.0001), and hospitalizations due to pertussis declined from 62 to 5 (P<.0001). Significant decreases in B. pertussis isolates and hospitalizations occurred in all age groups, including adults and nonvaccinated infants. Thus, mass vaccination of children with pertussis toxoid decreases spread of B. pertussis in the population.     

Whooping cough in adults: an update on a reemerging infection

Pertussis, or whooping cough, which is commonly thought of as a pediatric illness, is an underappreciated adult pathogen. Recent outbreaks highlight the significance of pertussis in adults and the risk of transmission to at-risk infants who are most susceptible to complications, including death. This article describes the recent epidemiologic shifts and reviews the clinical presentation, diagnosis, and treatment of pertussis. New vaccination recommendations by the Advisory Committee on Immunization Practices in response to recent outbreaks and infant deaths are highlighted.     

Patterns of susceptibility in an outbreak of Bordetella pertussis: Evidence from a community-based study

OBJECTIVE:

To describe an outbreak of Bordetella pertussis and to assess which factors were associated with the development of clinical pertussis in children and adults during the outbreak.

DESIGN:

A case series was described to define the epidemiology of the pertussis outbreak. A school-based survey of children was used to measure the incidence of clinical pertussis over the previous six months. Vaccination records from the local public health facility were used to look at the relationship between age and vaccination parameters, and susceptibility to clinically diagnosed pertussis. A cross-sectional survey of teachers, parents and some hospital workers was used to assess these associations in adults.

SETTING:

An outbreak of pertussis in an isolated northern community in British Columbia.

POPULATION STUDIED:

All children in the community who attend daycare, kindergarten or school, and their parents were surveyed. In addition, some health care workers and mothers of preschool children were surveyed.

MAIN RESULTS:

A total of 31 suspected cases of pertussis were identified over a three-month period. Ninety per cent of the affected children who had available vaccination records had received four or five doses of pertussis vaccine. Sixty per cent of the town''s 209 children returned completed surveys. Of these, 69% had available vaccination records. Thirty-six children (28%) reported symptoms that fit the case definition for pertussis over the previous three months. Attack rates were highest for the group of children aged 10 to 14 years. In a multivariate logistic regression analysis, receiving prophylactic medication and an increased number of years from the last vaccine dose were found to be significant predictors for developing pertussis. Thirty-four per cent of the estimated 291 adults in the community returned completed surveys. The attack rate of pertussis in the adults was only 9%. Being a member of the school staff and/or having a household contact with pertussis were significant predictors of developing pertussis.

CONCLUSIONS:

Immunity to pertussis appears to wane during childhood. Peak susceptibility appears to be during early adolescence. Adults do not seem to be at greater risk than adolescents for developing the disease, but it seems unlikely that this is due to better immunity. Rather, it is probably related to a lower risk of exposure to pertussis and a lower rate of progression to symptomatic disease when adults are infected.Key Words: Immunity, Pertussis, VaccinationVaccination against Bordetella pertussis has resulted in a dramatic reduction in the incidence of this disease in Canada. Outbreaks of pertussis, however, still occur. While many outbreaks reported elsewhere occur in populations where vaccination rates have declined, many others occur in populations with high vaccination coverage (1,2). This has not changed with the introduction of the acellular pertussis vaccine. The reasons for this are not clear, but waning immunity and the transmission of disease from adolescents and adults to younger children have been proposed as possible mechanisms (3,4). An additional constraint in studying this problem is that there is no known level of antibody that can be shown to be protective against developing pertussis (5).The idea of waning immunity has been challenged recently. De Serres and colleagues (6) found that the attack rates were the same in adolescent (12%) and adult (11%) household contacts of pertussis index cases. The authors (6) felt that this similar attack rate was more consistent with a decreasing proportion of susceptible subjects with age and with longlasting immunity. They did not suggest that this immunity comes solely from vaccination, but more likely from subclinical boosting from endemic disease. Clearly, this has implications as to the utility of introducing an adolescent booster dose to reduce further the incidence of disease in the population.In May 2000, an outbreak of pertussis was reported in an isolated northern community in British Columbia. Pertussis outbreaks have been known to occur in three- to five-year cycles in British Columbia. The last such outbreak occurred in 1996 and 1997, and resulted in more than 1100 reported cases. Increased rates of pertussis transmission had already been reported throughout the province since January 2000 (British Columbia Centre for Disease Control, internal report). By mid-May 2000, nearly 400 cases had been reported to the British Columbia Centre for Disease Control. Rates of infection were highest among young adolescents (aged 10 to 14 years), followed by older children (aged seven to nine years). The Northwest Coastal Health Services Society (the region that includes the town of Stewart) was not among those health regions that had previously reported increased numbers of cases.The town of Stewart, which has a population of approximately 500 people, has one health centre for both curative and preventive care, and is more than 150 km from the nearest settlement (excluding the hamlet of Hyder, Alaska, which is only 1.6 km away). There are three schools - a public primary school, a public secondary school and a small, private Christian school. The local health region and the Department of Health Care and Epidemiology at the University of British Columbia initiated an investigation of the pertussis outbreak in Stewart. It was thought that the relative isolation of the community and its small size would allow investigators to see whether immunization status, age and the length of time from the last vaccine dose would significantly affect disease attack rates. It was hoped that vaccination records for most of the town''s children could be verified and then compared with the results of a school-based survey for pertussis-like symptoms. As well, a survey of adults was undertaken to determine whether symptoms also occurred in this susceptible group, and whether this was related to recalled vaccination history. Disease control measures (7), including erythromycin prophylaxis of close contacts of index cases and enhanced surveillance among symptomatic individuals, had already been implemented before the present study was undertaken and were not interrupted during the course of the study.