Widespread paralytic poliomyelitis in Pakistan: A case-control study to determine risk factors and implications for poliomyelitis eradication.
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Despite substantial efforts to eradicate poliomyelitis by administering oral poliovirus vaccine through routine immunization and annual national immunization days (NIDs), Pakistan reported 22% (1147) of the worldwide cases in 1997. Reasons for continued high poliomyelitis incidence include failure to vaccinate, vaccine failure, or inadequate immunization strategies. A case-control study was conducted to measure vaccination status and reasons for undervaccination among 66 poliomyelitis cases and 130 age- and neighborhood-matched controls. Cases were undervaccinated through routine immunization (matched odds ratio [MOR], 0.3; 95% confidence interval [CI], 0.1-0.5); however, NID immunization was similar for cases and controls (MOR, 0.6; 95% CI, 0.3-1.2). Reasons for undervaccination included not being informed, considering vaccination unimportant, and long distances to vaccination sites. Failure to vaccinate through routine immunization was a major risk factor for poliomyelitis in Pakistan. Successful NIDs alone will not interrupt poliovirus circulation in Pakistan, and children remain at risk unless routine immunization is strengthened or additional supplementary immunization is provided. (+info)
Booster effect of Sabin poliomyelitis vaccine.
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Studies were carried out on 86 children aged 1-14 years who had titres of antibodies against poliovirus type 3 lower than 1: 32 and against type 2 higher than 1: 4. After a booster dose of poliomyelitis vaccine type 2+3, seroconversion took place in 44 (90%) of 49 children whose original titre was lower than 1: 4 and the geometrical mean titre increased to 1: 244. Of 37 children with low original titres of antibodies against type 3, i.e., 1: 4, 1: 8, or 1: 16, the titre increased fourfold or more in 31 (84%) and the geometrical mean titre rose to 1: 175. In 11 children (13%), no significant increase in titre took place. (+info)
Causes of low attendance at national immunization days for polio eradication in Bushenyi district, Uganda.
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The purpose of this study was to investigate the factors influencing attendance for polio National Immunization Days (NIDs) using the Attitudes-Social-influence-self-Efficacy (ASE) model as a guiding theoretical framework. The data was collected in Bushenyi district of south-western Uganda in 6 focus group discussions about outcomes of attendance at NIDs, about who decides on attendance, and about attendance barriers and supports. The purpose of NIDs - eradicating polio - was not known to the informants. The main reason mentioned for attending NIDs and other immunization was to weaken childhood diseases or to strengthen the children's capability in fighting diseases, whether they are immunizable or not. However, it was strongly believed that the previous NIDs had caused a severe malaria epidemic with a very high mortality, and this led to most parents not attending the next. Sources of social influence were mostly opinion and local leaders in communities, health workers, friends and relatives. Opinion leaders who did not immunize their children were said to hinder attendance at NIDs by other lay people. NIDs cards, on the other hand, were regarded as valuable means of support for attendance. Thus to improve immunization coverage, there is need for issuing NIDs cards, for using health education to change the belief that NIDs cause malaria, and to encourage local leaders to attend NIDs. (+info)
Evolution of circulating wild poliovirus and of vaccine-derived poliovirus in an immunodeficient patient: a unifying model.
(60/1057)
We determined nucleotide sequences of the VP1 and 2AB genes and portions of the 2C and 3D genes of two evolving poliovirus lineages: circulating wild viruses of T geotype and Sabin vaccine-derived isolates from an immunodeficient patient. Different regions of the viral RNA were found to evolve nonsynchronously, and the rate of evolution of the 2AB region in the vaccine-derived population was not constant throughout its history. Synonymous replacements occurred not completely randomly, suggesting the need for conservation of certain rare codons (possibly to control translation elongation) and the existence of unidentified constraints in the viral RNA structure. Nevertheless the major contribution to the evolution of the two lineages came from linear accumulation of synonymous substitutions. Therefore, in agreement with current theories of viral evolution, we suggest that the majority of the mutations in both lineages were fixed as a result of successive sampling, from the heterogeneous populations, of random portions containing predominantly neutral and possibly adverse mutations. As a result of such a mode of evolution, the virus fitness may be maintained at a more or less constant level or may decrease unless more-fit variants are stochastically generated. The proposed unifying model of natural poliovirus evolution has important implications for the epidemiology of poliomyelitis. (+info)
Expression of the human poliovirus receptor/CD155 gene during development of the central nervous system: implications for the pathogenesis of poliomyelitis.
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The gene for the human poliovirus receptor (hPVR/CD155) is the founding member of a new family of genes encoding proteins belonging to the immunoglobulin superfamily. To determine whether CD155 is expressed during mammalian development, we have made use of the previously characterized promoter of the CD155 gene and generated mice transgenic for a CD155 promoter-driven beta-galactosidase reporter gene. Expression of the reporter gene in transgenic embryos was observed during midgestation in anterior midline structures of the developing central nervous system and in the neuroretina. During that period, reporter gene expression appeared within the notochord and floor plate along the entire spinal cord reaching into the caudal diencephalon. In addition, transgene expression was observed in axonal projections emanating from retinal ganglion cells forming the optic nerve to reach the future region of the optic chiasm. Analysis of expression of CD155 during human embryonic development confirmed the distribution of reporter gene expression specified by CD155 promoter activity. The anatomical distribution of CD155 promoter activity during embryogenesis matches that of transacting factors previously identified to regulate transcription of the CD155 gene. Expression of CD155 within embryonic structures giving rise to spinal cord anterior horn motor neurons may explain the restrictive host cell tropism of poliovirus for this cellular compartment of the CNS. (+info)
Progress toward poliomyelitis eradication--South-East Asia Region, 1998-1999.
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In 1988, the World Health Assembly resolved to eradicate poliomyelitis by the end of 2000 (1). To achieve this goal, the 10 member countries of the World Health Organization (WHO) South-East Asia Region (SEAR) began implementing polio eradication strategies in 1994. In 1999, most polio cases worldwide were reported in SEAR (i.e., 48% of reported polio cases and 62% of cases with wild poliovirus isolation) (2,3). This report summarizes progress in achieving high routine and supplemental vaccination coverage, the surveillance of cases of acute flaccid paralysis (AFP), and the impact of these activities on polio eradication in the region during 1998-1999. (+info)
Vaccine-associated paralytic poliomyelitis: a retrospective cohort study of acute flaccid paralyses in Brazil.
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BACKGROUND: At the present time, in Brazil and other countries in the Americas, the only cases of paralytic poliomyelitis due to poliovirus are caused by vaccine strains. The recognition of possible determinants of vaccine-associated paralytic poliomyelitis (VAPP) by public health surveillance and immunization programmes is relevant to inform the debate on criteria for case definition and vaccination strategies. METHODS: A retrospective cohort study based on the cases of acute flaccid paralysis (AFP) reported to the Ministry of Health (MoH) was designed, with the objective of studying cases of VAPP in Brazil between 1989 and 1995. Clinical, laboratory and epidemiological data from 3656 acute flaccid paralysis (AFP) cases, 30 of them diagnosed as VAPP, were analysed. RESULTS: An 8.88 risk ratio of VAPP (95% CI : 4.37-18.03) was found when comparing individuals who received oral poliovirus vaccine (OPV) between 4 and 40 days before the onset of paralysis and individuals who did not receive the vaccine within this period. A risk of 1 case/2.39 million first doses and 1 case/13.03 million OPV doses administered was estimated for the general population. CONCLUSIONS: Cases of AFP who received OPV between 4 and 40 days before the onset of paralysis and had fever, a prodrome of gastrointestinal symptoms, history of first dose of OPV, isolation of vaccine poliovirus type 2, and young age deserve careful investigation, since they are at increased risk for the condition studied. (+info)
Effects of traditional classroom and distance continuing education: a theory-driven evaluation of a vaccine-preventable diseases course.
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OBJECTIVES: This study evaluated the effects of a major federal immunization continuing education course, delivered in both traditional classroom and satellite broadcast versions, on public health professionals' knowledge, agreement, self-efficacy, and adherence in practice to recommendations. METHODS: The study used a comparative time series design to determine whether the course influenced participants' knowledge, agreement, self-efficacy, and adherence in practice to general and polio-specific recommendations as measured immediately and 3 months after the course. It also compared the effects of the classroom and satellite broadcast versions and used path analysis to show how the outcomes were related to one another. RESULTS: Both versions significantly improved knowledge, agreement, self-efficacy, and adherence. Knowledge and agreement were significant predictors of self-efficacy, which directly predicted adherence. Vaccine availability and supportive clinic policies were also important adherence predictors. CONCLUSIONS: A well-designed training update can change provider knowledge, agreement, self-efficacy, and adherence. Traditional classroom and distance training can have comparable effects. The findings support incorporation of distance learning in national public health training, if the distance learning is used wisely in relation to training needs, goals, and practice contexts. (+info)