Similarities between the pathogenesis of and immunity to diphtheria and pertussis: the complex nature of serum antitoxin-induced immunity to these two diseases.
(17/815)
Despite data from animal studies, seroepidemiological surveys, and controlled clinical trials, skepticism persists about immunity to pertussis conferred by serum IgG neutralizing antibodies (antitoxin). This is largely prompted by the absence of a "protective" level of antitoxin. Examination of the similarities between the pathogenesis and immunity to pertussis and diphtheria provides an explanation for this dilemma. As with pertussis, diphtheria toxoid vaccination confers only approximately 70% immunity on an individual basis, individuals with protective levels of antitoxin may contract diphtheria, and about 50% of the entire population, especially adults, have less than protective levels of antitoxin. The virtual disappearance of diphtheria followed vaccination of the entire population with diphtheria toxoid, which blocked transmission of toxigenic Corynebacterium diphtheriae and thus reduced the pathogen to almost undetectable levels. The individual and community-based immunity induced by diphtheria toxoid, we hypothesize, is similar to that of pertussis and pertussis toxoid. (+info)
Making vaccination policy: the experience with rubella.
(18/815)
The massive rubella epidemic of 1962-1965 stimulated the development of rubella vaccine. Once vaccines were developed, the U.S. vaccination program, initially focused on infants and children, reduced both rubella and congenital rubella. However, later extension of vaccination to certain older age groups achieved significantly better control. While rubella clearly is not the perfect model for pertussis, a review of its history is illuminating. Current rubella vaccination policies resulted from an evolution in scientific understanding. Controversies, including those related to communicability, reactivity, and teratogenicity of the rubella vaccine virus, duration of immunity following vaccination, and protection following reinfection, led countries to use different approaches for national immunization programs. These differences were eventually resolved by clinical and epidemiological research coupled with rigorous scientific debate. Increased scientific understanding of pertussis, its epidemiology, and the effects of the new pertussis vaccines will similarly enable informed decision making on whether to extend pertussis immunization to adolescents and adults. (+info)
Pertussis in adults: epidemiology, signs, symptoms, and implications for vaccination.
(19/815)
Transmission of pertussis among adults is being increasingly recognized. About 1 or 2 in 1,000 adolescents and adults develop pertussis each year, > or = 12% of persons with acute cough illnesses of at least 1-2 weeks' duration have evidence of pertussis infection, and adults have been the source of pertussis for younger children. The advent of acellular pertussis vaccines, if safe and effective in adults, offers the opportunity to prevent transmission of pertussis in older populations. Several issues should be clarified before routine immunization is recommended, including the health burden of pertussis in adults and adolescents to be prevented by vaccination and how much morbidity resulting from pertussis in infants and children would be indirectly prevented. Preliminary studies suggest that pertussis vaccines are safe and immunogenic in adults. Potential recommendations for future vaccination might include all adolescents and adults at 10-year intervals along with the adult tetanus-diphtheria toxoids booster. Cost-benefit or cost-effectiveness analyses would be useful in developing vaccination policies for adults. (+info)
Changing epidemiology of pertussis in the United States: increasing reported incidence among adolescents and adults, 1990-1996.
(20/815)
Since 1990, the reported incidence of pertussis has increased in the United States with peaks occurring every 3-4 years. On the basis of analysis of pertussis cases reported to the Centers for Disease Control and Prevention, the incidence remained stable among children aged younger than 5 years, most of whom were protected by vaccination. In contrast to 1990-1993, during 1994-1996, the average incidence among persons aged 5-9 years, 10-19 years, and 20 years or older increased 40%, 106%, and 93%, respectively. Since 1990, 14 states reported pertussis incidences of > or =2 cases per 100,000 population during at least 4 years between 1990 and 1996; seven of these states also reported that a high proportion of cases occurred in persons aged 10 years or older. Analysis of national data on pertussis did not provide sufficient information to fully elucidate the relative importance of multiple possible explanations for the increase in the incidence of pertussis in adolescents and adults. Improvement in diagnosis and reporting of pertussis in this age group, particularly in some states, is an important factor contributing to the overall increase. (+info)
Epidemiological features of pertussis in hospitalized patients in Canada, 1991-1997: report of the Immunization Monitoring Program--Active (IMPACT).
(21/815)
To assess the morbidity associated with the continued high levels of pertussis, we studied all children <2 years of age who were admitted to the 11 Immunization Monitoring Program--Active (IMPACT) centers, which constitute 85% of Canada's tertiary care pediatric beds. In the 7 years preceding implementation of acellular pertussis vaccine, a total of 1,082 pertussis cases were reported, of which 49.1% were culture-confirmed. The median age of the patients was 12.4 weeks; 78.9% of cases were in children <6 months of age. Complications of pertussis were common: pneumonia was reported in 9.4% of cases, new seizures in 2.3%, and encephalopathy in 0.5%. There were 10 deaths (0.9%), all in children < or =6 months of age. Duration of hospitalization was longer (9.3 days vs. 4.9 days; P = .001) and intensive care was required more frequently (19.2% vs. 4.9%; P = .001) in infants under <6 months of age than in those > or =6 months. Pertussis continues to cause significant morbidity and occasional mortality in Canada, particularly in young infants. (+info)
Parapertussis and pertussis: differences and similarities in incidence, clinical course, and antibody responses.
(22/815)
OBJECTIVES: To compare the incidence, clinical course, and serologic response to Bordetella antigens in patients with parapertussis and pertussis. DESIGN: Two studies were performed in Sweden during the 1990s, when pertussis vaccines were used only in clinical trials. Study I was a retrospective study of patients with positive Bordetella cultures obtained in clinical routine, and study II involved an active search for patients with Bordetella infections during a placebo-controlled trial of a pertussis toxoid vaccine. RESULTS: Study I includes 58, and study II 23 patients with parapertussis. In study I, the incidence of parapertussis was 0.016 cases per 100 person years in children 0 to 6 years old and 0 in older children and adults. In study II, the incidence rates of parapertussis and pertussis were 0.2 and 16.2 per 100 person years, respectively, in children followed from 3 months to 3 years of age. The median number of days with cough was 21 in parapertussis and 59 in pertussis. The proportions of children with whooping and vomiting were lower in parapertussis than in pertussis. Geometric mean serum filamentous hemagglutinin IgG increased from 6 to 63, and pertactin IgG from 4 to 12 units/mL in parapertussis patients, which was similar to increases in children with pertussis. CONCLUSIONS: Disease caused by Bordetella parapertussis is diagnosed less commonly and is milder and of shorter duration than disease caused by Bordetella pertussis. Parapertussis induced serum IgG against filamentous hemagglutinin and pertactin of similar magnitude as does pertussis, and did not induce serum IgG against pertussis toxin. (+info)
Antigenic variants in Bordetella pertussis strains isolated from vaccinated and unvaccinated children.
(23/815)
Bordetella pertussis shows polymorphism in two proteins, pertactin (Prn) and the pertussis toxin (PT) S1 subunit, which are important for immunity. A previous study has shown antigenic shifts in these proteins in the Dutch B. pertussis population, and it was suggested that these shifts were driven by vaccination. The recent Italian clinical trial provided the opportunity to compare the frequencies of Prn and PT S1 subunit variants in strains isolated from unvaccinated children, and from children vaccinated with two acellular and one whole-cell pertussis vaccine. Four Prn variants (Prn1, Prn2, Prn3 and Prn5) were found in the 129 strains analysed. Prn1, Prn2 and Prn3 have been described previously, whereas Prn5 is a novel variant. Prn1, Prn2, Prn3 and Prn5 were found in, respectively, 6, 41, 51 and 2% of the strains. The B. pertussis strains used to produce the vaccines administered in the clinical trial were found to produce Prn1, or a type which differed from Prn1 in one amino acid. The frequency of the Prn1 variant was found to be lowest in the strains isolated from vaccinated groups, suggesting that Prn1 strains are more affected by vaccine-induced immunity than Prn2 and Prn3 strains. Only one PT S1 type (S1A) was observed in the examined strains, which was distinct from the types produced by the vaccine strains (S1B and S1D). The S1A type also predominates in the Dutch B. pertussis population. The genetic relationship among B. pertussis strains analysed by IS1002-based DNA fingerprinting revealed that three fingerprint types predominate, representing more than 70% of the strains. Prn2 strains showed a greater variety of fingerprint types compared to Prn3, suggesting that Prn3 has emerged more recently. The results are discussed in the light of vaccine-driven evolution. (+info)
Genomic plasticity in natural populations of Bordetella pertussis.
(24/815)
We determined the genomic organization of 14 clinical strains of Bordetella pertussis isolated over an 18-month period in Alberta, Canada. The maps of these 14 strains, while demonstrating general similarity of gene order, display a number of examples of genomic rearrangements in the form of large chromosomal inversions. (+info)