La vacuna polio oral en lactantes no interfiere con la detección de enterovirus en sangre / Oral polio vaccine in infants does not interfere in detection of enterovirus in blood

Introduction: There is not known if a viraemia post-oral polio vaccine (OPV) is detectable by modern molecular techniques. Such viraemia could affect the performance of the real time-polymerase chain reaction (PCR) for non polio enterovirus (EV) detection, technique of growing clinical use for the study of febrile infants. Objective: To determine viraemia post-first dose of OPV in healthy infants, by molecular techniques. Patients and Methods: 50 infants less than three months without previous VPO were randomized in 5 groups: a control group with pre-vaccination blood sample (BS), group 1 BS at day 2, group 2 BS at day 4, group 3, BS at day 6 and group 4, BS at day 8 post-vaccination. Conventional and specific PCR for poliovirus and real time PCR for non polio EV were performed in BS and in OPV samples. Results: No genetic material of poliovirus was detected in any infant, while in 9 of them (18%) non polio EV was identified. Real time PCR for EV did not amplify poliovirus from OPV samples. Discussion: Results suggest that no post VPO viraemia detectable by molecular methods exists. Considering that real time PCR for EV does not allow to identify polio virus, no false positives of the test are expected as a result of a recent VPO vaccination. We documented presence of non polio EV in blood of healthy asymptomatic infants.

Introducción: No existen estudios que indiquen si la vacuna polio oral (VPO) produce viremia detectable mediante métodos moleculares. Una eventual viremia podría afectar el rendimiento de la RPC tiempo real para detectar enterovirus (EV) no polio, examen de creciente uso clínico en lactantes pequeños con fiebre sin foco. Objetivo: Determinar viremia post VPO en lactantes sanos, por métodos moleculares. Métodos: 50 menores de 3 meses, al momento de recibir su primera VPO se distribuyeron en forma aleatoria en 5 grupos: control, muestra de sangre pre-vacunación; grupo 1, muestra al 2° día; grupo 2, al 4° día; grupo 3, al 6° día y grupo 4, al 8° día post-vacunación. Se realizó RPC convencional específica para virus polio y RPC tiempo real para EV no polio en las muestras de sangre y en muestras de VPO. Resultados: No se identificó presencia de material genético de virus polio en lactante alguno, mientras que en 9 (18%) se identificó presencia de EV no polio. La RPC tiempo real para EV no polio no amplificó material genético a partir de las muestras de VPO. Discusión: Los resultados sugieren que no existe viremia post-VPO detectable por métodos moleculares. Considerando que la RPC tiempo real de EV no polio de uso clínico no permite identificar la presencia de virus polio, estos hallazgos indican que no existirán falsos positivos de este examen como resultado de una vacunación VPO reciente. Adicionalmente se documentó presencia de EV no polio en sangre de lactantes asintomáticos.

A RT-PCR method for selective amplification and phenotypic characterization of all three serotypes of Sabin-related polioviruses from viral mixtures

Outbreaks caused by vaccine-derived polioviruses are challenging the final eradication of paralytic poliomyelitis. Therefore, the surveillance of the acute flaccid paralysis cases based on poliovirus isolation and characterization remains an essential activity. Due to the use of trivalent oral poliovirus vaccine (OPV), mixtures containing more than one serotype of Sabin-related polioviruses are frequently isolated from clinical samples. Because each poliovirus isolate needs to be individually analyzed, we designed polymerase chain reaction primers that can selectively distinguish and amplify a genomic segment of the three Sabin-related poliovirus serotypes present in mixtures, thus, optimizing the diagnosis and providing prompt information to support epidemiologic actions.

Immunogenicity study for tetra and penta component vaccines in infants

A randomized controlled trial to evaluate the immunogenicity of combined Hemophilus Influenzae type b with DTP +/- injectable polio vaccine and the immunogenicity of giving one injectable polio vaccine combined with the first of 3 doses of oral polio vaccine. After parental consent, infants were randomized into 4 groups to receive the following vaccines; First group: Single Hemophilus Influenzae type b vaccine [PRP-T, Act-HIB[registered] in addition to DPT and oral polio vaccine. Second group: Combined [PRP-T+DTP] TETRAct-HIB[registered] and oral polio vaccine. Third group: First dose is combined [PRP-T+DPT+injectable polio vaccine] PENTAct-HIB[registered] and oral polio vaccine. Then, the 2nd and 3rd dose is TETRAct-HIB[registered] and oral polio vaccine. Fourth group: DPT and oral polio vaccine only [Control group]. Vaccines were given at 6 weeks, 3 months and 5 months. Blood samples were collected from all children, one month after the 3rd dose at the age of 6 months. Samples were sent for laboratory assay for anti-PRP, Diphtheria anti-toxin, Tetanus anti-toxin, polio antibody type 1, 2 and 3 and pertussis Agglutinins. Single Hemophilus Influenzae type b vaccine produced a higher anti-PRP level [15 ug ml[-1]] compared to combined Hemophilus Influenzae type b vaccine, [9.5 ug ml[-1]] in the second group and [11 ug ml[-1]] in the 3rd group but without significant level. It was found that 90% of non-vaccinated children in our sample are lacking the protective level against Hemophilus Influenzae type b diseases. Giving injectable polio vaccine with oral polio vaccine in the first of 3 doses did not affect the level of polio antibody for the 3 poliovirus types but positivity after the 3 polio doses increased compared to previous studies. In the 4 groups, 100% of the children achieved the protective level against Pertussis, Tetanus and 95% for Diphtheria. No significant negative interaction was found between vaccine antigens used in the study. Combined vaccines are effective methods to include Hemophilus Influenzae type b and injectable polio vaccine in the Extended Program of Immunization without unacceptable decrease in immunogenicity of each component

Poliomyelitis: immune status of the populotion of Kuwait

A comprehensive program to immunize children against polioviruses was started in Kuwait in 1976. This report is the first laboratory study aimed at investigating the immune status of the population of Kuwait to polioviruses. By using a virus neutralization procedure, the prevalence and the titer of poliovirus-specific antibodies were determined in 759 serum samples. Samples represented the following age groups: 0-1 months, 1-9 years, 10-19 years, 20-29 years, 30-39 years and 40-60 years. The first two age groups, during which the polio vaccinations are given, were studied in detail. Results allow for the following conclusions: [1] Monovalent [type 1] polio vaccine, given at birth, has an impact on the early development of immunity. It prevents the drop in the [maternal] antibody level during the first 2 months of life. [2] Immunity to all three types of polioviruses reaches a high level at the age of 5-6 months. [3] Both the prevalence and the level of antibody remain high in older age groups. The data reported here prove that the use of trivalent oral polio vaccine along with an efficient vaccination coverage has led to the complete elimination of paralytic poliomyelitis in Kuwait. Maintaining the polio-free status requires laboratory monitoring of the antibody level and nature of circulating poliovirus strains

The value of potency testing of poliomyelitis and measles vaccines as an integral part of cold chain surveillance.

The Virology Division in the Institute for Medical Research, Kuala Lumpur, Malaysia performs potency tests on oral polio vaccines and live attenuated measles vaccines. Since these potency tests were introduced in 1981 a total of 752 tests have been performed on vaccine samples from peripheral immunization centers. Of 165 representative vaccine samples sent for potency evaluation after a cold chain breakdown 154 (87%) passed minimum potency requirements recommended for immunization of infants. In the absence of potency evaluation, those vaccines exposed to temperatures higher than the recommended storage range would be discarded, perhaps resulting in unnecessary wastage and economic loss. Results of the vaccine potency evaluation has enabled health authorities to indirectly monitor cold chain efficiency and ensure the high quality of viral vaccines used in our childhood immunization program.

Antibody response of children immunized with poliovaccines: an evaluation using two strains of poliovirus type 1.

Neutralizing antibody response of children immunized with either OPV (3 doses), or IPV (2 doses) was evaluated against poliovirus type 1 Sabin vaccine strain and a local neurovirulent isolate. Both vaccines elicited significantly better antibody response against the vaccine strain than against the neurovirulent isolate. Moreover, approximately 35 per cent of sera contained very low levels of antibody against the virulent virus in spite of good antibody titre against the vaccine strain. The observed difference in antibody response to the wild and the vaccine strains was significant. The differential immune response could be one of the reasons of paralytic disease observed even after administration of OPV (3), in some children if infecting virus dose is high, as in case of urban slums in endemic areas.

Antibody response to three doses of standard and double dose of trivalent oral polio vaccine.

The study was undertaken to compare the antibody response of 6-12 weeks old infants after three doses of standard trivalent oral polio vaccine (TOPV) (Groups A; (n = 42) with three doses of double the amount of TOPV (Group B; n = 35). Seroconversions in Group A were 64.2, 80.9% and 57.1% for Types I, II and III polioviruses, respectively. The corresponding figures for Group B were 77.7, 80.0 and 60.6%, respectively, the differences being insignificant. Differences in feeding practices and presence of maternal antibodies did not affect seroconversion. This suggests that increasing the amount of vaccine virus in each dose is not an alternative to present strategy. Breast feeding and presence of maternal antibodies are not responsible for poor seroconversion.

Polio immunization and serological status in children and adolescents in Jamaica 1985

A survey of immunization status and serological immunity to polio was carried out in 5 parishes in Jamaica in 1985. A sample of 2,506 children and adolescents aged 1 - 19 years was chosen by selecting clusters of children in enumeration districts (EDs) in each parish from the 1980 Census. Immunization status was verified by examining immunization records. Serological assay for antibodies to Polio Types 1, 2 =, and 3 was done. A positive neutralization test at dilution of 1:8 was done. A positive neutralization test at dilution of 1:8 was taken as immunity to the polio virus. Of the 1,819 children whose immunization status was confirmed, coverage with 3 or more doses of roral polio vaccine was highest in the 1 - 4 year age group with with 79.7% and lowest in the 15 - 19-year age group with 37.4%. Of the 2,506 children 81.4%, 94.7% and 72.3% were seropositive for Polio Types 1, 2 and 3 respectively. There was a significant difference in the prevalence of seropositives between individuals with and those without a history of vaccinations. No urban/rural or sex differences were noted. The study indicated a higher level of immunization status than previous surveys and a high level of serological immunity to polio

Enterovirus survey before and after poliomyelitis vaccination in Kuala Lumpur, Malaysia.

Stool samples from healthy children mainly of the low income group aged 0 to 7 years of age from five Maternal and Child Health Centres in Kuala Lumpur were obtained for isolation of enteroviruses. The specimens were collected before and after the mass vaccination given in the face of polio type 1 epidemic which started in October, 1971. The prevelance rate of enteroviruses was 11.9% (3.0% polioviruses, 8.9% non-polio enteroviruses) before the vaccination and essentially the same after. Coxsackie A viruses predominated over the other enteroviruses in the pre- and post-vaccination phases. The highest isolation rate of enteroviruses was observed in children 0 to 2 years age. No significant differences in distribution by sex, race and month were noted. A sharp fall in the prevalence rates of total enteroviruses and polioviruses was noted shortly after the mass vaccination campaign However, the rates reverted to the pre-vaccination state during the next successive years.