Progress toward poliomyelitis eradication--South-East Asia Region, 1998-1999.
(33/545)
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.
(34/545)
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)
Natural genetic exchanges between vaccine and wild poliovirus strains in humans.
(35/545)
In a previous study of poliovirus vaccine-derived strains isolated from patients with vaccine-associated paralytic poliomyelitis (VAPP) (9, 11), we reported that a high proportion (over 50%) of viruses had a recombinant genome. Most were intertypic vaccine/vaccine recombinants. However, some had restriction fragment length polymorphism (RFLP) profiles different from those of poliovirus vaccine strains. We demonstrate here that five such recombinants, of 88 VAPP strains examined, carried sequences of wild (nonvaccine) origin. To identify the parental wild donor of these sequences, we used RFLP profiles and nucleotide sequencing to look for similarity in the 3D polymerase-coding region of 61 wild, cocirculating poliovirus isolates (43 type 1, 16 type 2, and 2 type 3 isolates). In only one case was the donor identified, and it was a wild type 1 poliovirus. For the other four vaccine/wild recombinants, the wild parent could not be identified. The possibility that the wild sequences were of a non-poliovirus-enterovirus origin could not be excluded. Another vaccine/wild recombinant, isolated in Belarus from a VAPP case, indicated that the poliovirus vaccine/wild recombination is not an isolated phenomenon. We also found wild polioviruses (2 of 15) carrying vaccine-derived sequences in the 3' moiety of their genome. All these results suggest that genetic exchanges with wild poliovirus and perhaps with nonpoliovirus enteroviruses, are also a natural means of evolution for poliovirus vaccine strains. (+info)
Vaccine-associated paralytic poliomyelitis: a case report of domiciliary transmission.
(36/545)
Poliomyelitis associated with live strain vaccine is defined as the paralytic form of the acute anterior poliomyelitis related to the vaccine strain. Since these strains behave similarly to the wild-type virus, we can differentiate, epidemiologically, two types of vaccine-associated poliomyelitis: cases in which the patient was vaccinated and cases in which the patient had had contact with vaccinated individuals. We herein present the case of an unvaccinated child, with a clinical picture of an acute anterior poliomyelitis associated with the live strain vaccine, whose brother received the Sabin vaccine 20 days before the onset of the symptoms. Vaccine strain of the type 3 poliovirus was isolated in fecal culture and a presented mutation in nucleotide 472 (C-->U) in the 5' non-coding region, which is strongly related to the higher strain virulence. (+info)
Trial of a supplemental dose of four poliovirus vaccines.
(37/545)
BACKGROUND: The immunogenicity of oral poliovirus vaccine (OPV), particularly the type 3 component, is lower in infants in most developing countries than in infants in industrialized countries. We conducted a multicenter trial in Oman to evaluate the response to a supplemental dose of four poliovirus vaccine formulations. METHODS: At nine months of age, infants were randomly assigned to receive inactivated-poliovirus vaccine (IPV), administered subcutaneously; trivalent OPV manufactured in the United States or in Europe; or monovalent type 3 OPV. Serum samples were collected at enrollment and 7 and 30 days later. All of the infants had previously received five doses of OPV. RESULTS: We enrolled 1025 infants; 785 (76.6 percent) met all the study requirements. At enrollment, 96.8 percent of the infants were seropositive for poliovirus type 1, 98.0 percent for type 2, and 88.0 percent for type 3. At 30 days there were no significant increases in type 3 seroprevalence or in the median antibody titer in the groups of infants who received OPV. Among the recipients of IPV, type 3 seroprevalence increased from 87.8 percent at enrollment to 97.1 percent at 30 days (P<0.001), and the median antibody titer increased from 1:228 to 1:1448 or higher (P<0.001). The rapid initial increase in the antibody titer suggests a secondary immune response. CONCLUSIONS: A supplemental dose of IPV has excellent immunogenicity and leads to increases in the titer of antibodies against type 3 poliovirus, whereas supplemental doses of the oral vaccines do not have these effects. (+info)
Molecular and antigenic characterization of a highly evolved derivative of the type 2 oral poliovaccine strain isolated from sewage in Israel.
(38/545)
An unusual, highly diverged derivative of the Sabin type 2 oral poliovaccine (OPV) strain was recovered from environmental samples during routine screening for wild polioviruses. Virus was cultivated in L20B cells and then passaged on BGM cells at 40 degrees C (RCT [reproductive capacity at supraoptimal temperature]-positive marker) to select against most OPV strains. All but 1 of 25 RCT-positive OPV-derived environmental isolates were antigenically and genetically (>99.5% VP1 sequence match) similar to the respective Sabin strains. However, isolate PV2/4568-1/ISR98 (referred to below as 4568-1) escaped neutralization with Sabin 2-specific monoclonal antibodies and cross-adsorbed sera, and had multiple nucleotide substitutions (220 of 2,646; 8.3%) in the P1 capsid region. Fourteen of the 44 associated amino acid substitutions in the capsid mapped to neutralizing antigenic sites. Neutralizing titers in the sera of 50 Israeli children 15 years old were significantly lower to 4568-1 (geometric mean titer [GMT], 47) than to Sabin 2 (GMT, 162) or to the prototype wild strain, PV2/MEF-1/EGY42 (GMT, 108). Two key attenuating sites had also reverted in 4568-1 (A(481) to G in the 5' untranslated region and the VP1 amino acid I(143) to T), and the isolate was highly neurovirulent for transgenic mice expressing the poliovirus receptor (PVR-Tg21 mice). The extensive genetic divergence of 4568-1 from the parental Sabin 2 strain suggested that the virus had replicated in one or more people for approximately 6 years. The presence in the environment of a highly evolved, neurovirulent OPV-derived poliovirus in the absence of polio cases has important implications for strategies for the cessation of immunization with OPV following global polio eradication. (+info)
In 1988, the World Health Assembly resolved to eradicate poliomyelitis globally by 2000 (1). Following the signing of the Yaounde Declaration on Polio Eradication in Africa in 1996, Ethiopia joined global efforts toward polio eradication (2). Since then, Ethiopia has accelerated implementation of polio eradication strategies. This report summarizes progress toward polio eradication in Ethiopia during 1997-August 2000 and highlights the remaining challenges toward achieving the goal. (+info)
Assessment of poliovirus eradication in Japan: genomic analysis of polioviruses isolated from river water and sewage in toyama prefecture.
(40/545)
Seventy-eight poliovirus strains isolated from river water and sewage in Toyama Prefecture, Japan, during 1993 to 1995 were characterized by the PCR-restriction fragment length polymorphism (RFLP) method and by partially sequencing the VP3 and VP1 regions of the viral genome. Of these isolates, 36 were identified as Sabin vaccine strains, and 42 were identified as vaccine variant strains that had less than 1.4% nucleotide divergence from the Sabin strains, including 7 isolates with patterns different from those of Sabin strains as determined by PCR-RFLP analysis. These findings suggest that wild-type poliovirus was not circulating in Toyama Prefecture. (+info)