A model-based evaluation of the national immunization programme against rubella infection and congenital rubella syndrome in The Netherlands.
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In order to improve the prevention of cases of congenital rubella syndrome in The Netherlands, in 1987 the selective vaccination strategy against rubella infection in girls was replaced by mass vaccination. This decision was supported by mathematical model analyses carried out by Van Druten and De Boo. In order to compare the predicted impact of the rubella vaccination programme with the current available data in more detail, a similar model was built. Although the model predicts elimination of the rubella virus, data show that virus circulation is still present at a higher level than expected by the model. Simulation studies indicate that import of infection and a lower vaccine effectiveness, related to possible asymptomatic reinfection of vaccinated people, could be sources contributing to the present virus circulation. Even though the number of infections is much higher than the number of reported cases of disease, limited serosurveillance data and case notification data show that females of childbearing age are well protected by immunization. (+info)
Interrupting the transmission of respiratory tract infections: theory and practice.
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Interruption of transmission has always been one of the most attractive approaches for infection control. The technologies available were severely limited before the development of appropriate vaccines. Mathematically, the proportion of those who need to be immune to interrupt transmission can be derived from the Ro, which represents the number of new cases infected by a single case when all contacts are susceptible. Purely respiratory infections have critical characteristics affecting transmission that are different from key childhood vaccine-preventable diseases spread by the respiratory route. They include frequent reinfections and antigenic changes of the agents. Pragmatic approaches to understanding their potential effect can be found in experimental and programmatic use of vaccines such as those for Haemophilus influenzae type b and influenza virus infections. Results of these experiences can in turn strengthen the development of transmission theory. (+info)
Making vaccination policy: the experience with rubella.
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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)
Infant vaccinations and risk of childhood acute lymphoblastic leukaemia in the USA.
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Previous studies have suggested that infant vaccinations may reduce the risk of subsequent childhood leukaemia. Vaccination histories were compared in 439 children (ages 0-14) diagnosed with acute lymphoblastic leukaemia (ALL) in nine Midwestern and Mid-Atlantic states (USA) between 1 January 1989 and 30 June 1993 and 439 controls selected by random-digit dialing and individually matched to cases on age, race and telephone exchange. Among matched pairs, similar proportions of cases and controls had received at least one dose of oral poliovirus (98%), diphtheria-tetanus-pertussis (97%), and measles-mumps-rubella (90%) vaccines. Only 47% of cases and 53% of controls had received any Haemophilus influenzae type b (Hib) vaccine (relative risk (RR) = 0.73; 95% confidence interval (CI) 0.50-1.06). Although similar proportions of cases (12%) and controls (11%) received the polysaccharide Hib vaccine (RR = 1.13; 95% CI 0.64-1.98), more controls (41%) than cases (35%) received the conjugate Hib vaccine (RR = 0.57; 95% CI 0.36-0.89). Although we found no relationship between most infant vaccinations and subsequent risk of childhood ALL, our findings suggest that infants receiving the conjugate Hib vaccine may be at reduced risk of subsequent childhood acute lymphoblastic leukemia. Further studies are needed to confirm this association and, if confirmed, to elucidate the underlying mechanism. (+info)
Opportunistic immunisation in hospital.
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AIM: To assess the potential for administering catch up and scheduled immunisations during hospital admission. METHODS: Immunisation status according to the child's principal carer was checked against official records for 1000 consecutively admitted preschool age children. Junior doctors were instructed to offer appropriate vaccination before discharge, and consultants were asked to reinforce this proactive policy on ward rounds. RESULTS: Excluding those children who were not fully immunised against pertussis through parental choice, 142 children (14.2%) had missed an age appropriate immunisation and 41 were due a scheduled immunisation. None had a valid contraindication. Only 43 children were offered vaccination on the ward but uptake was 65% in this group. CONCLUSIONS: Admission to hospital provides opportunities for catch up and routine immunisations and can contribute to the health care of an often disadvantaged group of children. These opportunities are frequently missed. Junior doctors must be encouraged to see opportunistic immunisation as an important part of their routine work. (+info)
Decay of passively acquired maternal antibodies against measles, mumps, and rubella viruses.
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The decay of maternally derived antibodies to measles, mumps, and rubella viruses in Swiss infants was studied in order to determine the optimal time for vaccination. A total of 500 serum or plasma samples from infants up to 2 years of age were tested by enzyme-linked immunosorbent assay and fluorescent-antibody testing. The decline of antibody prevalence was slowest against the measles virus. By 9 to 12 months of age, only 5 of 58 (8.6%; 95% CI, 2.9 to 19.0) infants were antibody positive for the measles virus, and only 2 had levels above 200 mIU/ml. Mumps and rubella virus antibody seropositivity was lowest at 9 to 12 months of age with 3 of 58 (5. 2%; 95% CI, 1.1 to 14.4) infants and at 12 to 15 months with 1 of 48 (2.1%; 95% CI, 0.1 to 11.1) infants, respectively. Concentrations of passively acquired antibodies decreased rapidly within the first 6 months of life. We observed no significant differences in antibody prevalence or concentration according to gender in any age group. In conclusion, MMR vaccination at 12 instead of 15 months of age could reduce the pool of susceptible subjects in infancy and support the efforts to eliminate these infections, particularly in combination with a second vaccine dose before school entry. (+info)
Kawasaki disease: a maturational defect in immune responsiveness.
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Kawasaki disease (KD), an acute febrile disease in children of unknown etiology, is characterized by a vasculitis that may result in coronary artery aneurysms (CAAs). In new patients with KD, a selective and prolonged T cell unresponsiveness to activation via the T cell antigen receptor CD3 was observed, whereas proliferation to other stimuli was intact. This "split T cell anergy" delineated KD from other pediatric infections and autoimmune diseases and correlated with CAA formation (P<.001). A transient immune dysfunction was also suggested by an incomplete responsiveness to measles-mumps-rubella (MMR) vaccination in patients with KD versus controls (P<.0001; odds ratio, 15.6; 95% confidence interval, 4.8-51.1), which was overcome by revaccination(s). The reduced responsiveness to MMR in patients with KD suggests a subtle and predetermining immune dysfunction. An inherent immaturity to clear certain antigens may be an important cause that precipitates KD and the immune dysregulation during acute disease. (+info)
Infection with wild-type mumps virus in army recruits temporally associated with MMR vaccine.
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Four cases of mumps were reported among 180 army recruits who had received MMR vaccine 16 days earlier. Mumps serology, salivary mumps IgM and PCR tests for the SH gene were performed on the 4 cases and on 5 control recruits who remained well. PCR products were sequenced and the sequences compared to those of wild type and vaccine strains of mumps. Further salivary mumps IgM tests were performed on the remaining 171 recruits. Mumps infection was confirmed in the 4 cases but not in the 5 controls. The controls had serological evidence of prior immunity. The SH gene sequence found in the 4 cases was wild type. Saliva tests identified 2 additional recruits with mumps IgM, one of whom had presented with suspected mumps 2 days before the MMR vaccine was given. Thus 6 (5 symptomatic and 1 asymptomatic) cases of mumps in army recruits recently receiving MMR vaccine were not due to the vaccine but to coincidental infection with wild-type mumps virus. The probable index case was revealed by salivary mumps IgM tests. This study highlights the importance of appropriate investigation of illness associated with MMR vaccination. (+info)