RESUMO
A considerable number of field trials have been published over the last 30 years, showing measles vaccines to be highly effective. Due to inconsistencies in methodology, comparisons between these studies have often been difficult with regard to the potencies used and the sero-response of vaccinated children. This article reviews key studies which have measured the response of children to different potencies of vaccine. The review concludes that increasing the titre of vaccine above log10 3.0 does not appear to improve vaccine efficacy. It is recommended that standard titre measles vaccine should be administered with a minimum potency of log10 3.0 TCID50 or PFU per dose at 9 months of age or later. This recommendation is endorsed by the Global Advisory Group and the Research and Development Group of the Expanded Programme on Immunization.
Assuntos
Vacina contra Sarampo/imunologia , Criança , Pré-Escolar , Relação Dose-Resposta Imunológica , Humanos , LactenteRESUMO
Due to persistence of poliomyelitis cases in the Pacific Coast of Mexico and particularly in the state of Sinaloa, a house to house vaccination strategy named "Sinaloa Operation" was carried out in 100% of the territory of this state. Sinaloa was divided in small geographical and statistical unit area (AGEB). Simultaneously, teams of nurse carried out a population census of children under five years old and pregnant women. Nurses vaccinated the children with Sabin trivalent vaccine in undiscriminating form. These activities were made in three phases. In the last phase (February 1991) 301, 441 Sabin vaccine doses were administered. This figure represents an extension of the vaccination coverage to the children of the seasonal migrant workers from other parts of the country. As a result of this programme. Sinaloa has not had any other polio case since two years ago.
Assuntos
Poliomielite/prevenção & controle , Vacina Antipólio de Vírus Inativado/administração & dosagem , Vacinação/métodos , Pré-Escolar , Humanos , Lactente , México , Avaliação de Programas e Projetos de Saúde , População Rural , População UrbanaRESUMO
General aspects on the immune response to poliovirus are described, considering it's molecular structure. Since the poliovirus is a cytocide agent, antibody immune response is the most important among those related to protection; however probably a minimum of helper T cells are required (more than 200 T lymphocytes with phenotype CD4) in order to get a best response. Phagocyte, NK cells and T lymphocytes probably take part in the viral clearance from the central nervous system, also in the host injure mechanisms. Some molecular aspects of the neutralizing antibodies combining site are described too. Activation particularities, of the common mucosal immune system confirm the importance of the secretory immune response in the control of the poliomyelitis.
Assuntos
Poliomielite/imunologia , Poliovirus/imunologia , Formação de Anticorpos , Criança , Epitopos/imunologia , Humanos , Imunidade Celular , Interferons/imunologia , Mucosa/imunologia , Poliomielite/transmissão , Poliovirus/fisiologia , Replicação ViralAssuntos
Vacina contra Sarampo , Sarampo/mortalidade , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , México/epidemiologia , MorbidadeRESUMO
Study results of passive natural immunity anti-measles, and immune response to measles vaccine from different strains in Mexican children under one year old, are described in this paper. Mexican infants in these studies ended their maternal immunity at 8-10 months of age. Edmonston-Zagreb (EZ) vaccine strain had higher seroconversion rates comparing to Schwarz strain. Dose response effect was more closely related to Schwarz strain than EZ, since difference in seroconversion rates with standard, medium and high doses were statistically significant. However geometric mean post-vaccination titers were higher in children vaccinated with Schwarz strain, than EZ receptors.
Assuntos
Vacina contra Sarampo/imunologia , Sarampo/imunologia , Criança , Pré-Escolar , Humanos , Imunidade Materno-Adquirida , Lactente , Sarampo/epidemiologia , Sarampo/prevenção & controle , Vírus do Sarampo/classificação , Vírus do Sarampo/imunologia , México/epidemiologia , Especificidade da EspécieRESUMO
In order to evaluate the quality of the measles vaccine, it was carried out a study in three states of Mexico (Durango, San Luis Potosi and Yucatan) during the intensive vaccination campaign in 1986. Edmonston-Zagreb measles vaccine vials were obtained from the different administrative-sanitary levels of the Ministry of Health in Mexico. Interviews were performed to the vaccine responsibles. Questionnaires had the following aspects of the cold chain: storage, preservation, control and transport of measles vaccine. Answers were evaluated through a system, where 100% indicated the necessary and sufficient level to get a good operating of the cold chain. The vaccine potency did not have variations under the minimum titre recommended for the World Health Organization (W.H.O.). The three states had the following compliment of the cold chain norms: 1) Central state level: 83% in storage, 80% in preservation, 100% in control and 100% in transport norms; 2) Regional level (jurisdiction): 87% in storage, 51% in preservation, 93% in control and 100% in transport norms; 3) Local level: 83% in storage, 64% in preservation, 83% in control and 33% in transport norms.
Assuntos
Vacina contra Sarampo/imunologia , Temperatura Baixa , Estabilidade de Medicamentos , Armazenamento de Medicamentos/normas , Estudos de Avaliação como AssuntoRESUMO
An evaluation of the cold chain used during the "National Vaccination Days Against Poliomyelitis" in January and March of 1987 and 1988 was performed in 32 states of Mexico, both the potency of the trivalent Sabin vaccine and completion of requirements for the maintenance of the cold chain were evaluated at each level in the Ministry of Health's structure. Only 56 percent of the refrigeration units exclusively stored vaccines, more than 10 percent of refrigerators were broken, and 44 percent of the persons responsible for the cold chain system considered the storage capacity inadequate. A correlation was found between non-fulfillment of maintenance requirements for cold chain and a decreased in vaccine potency.
Assuntos
Armazenamento de Medicamentos/normas , Vacina Antipólio Oral/análise , Refrigeração/normas , Estabilidade de Medicamentos , Estudos de Avaliação como Assunto , Humanos , México , Controle de QualidadeRESUMO
Among primary health care programs, one of those that has the highest benefit/cost ratio is measles immunization. An estimate of cases, complicated cases and deaths that could have occurred if such immunization program would not have been run, and costs of medical care (hospitalization, physician's visits, medical treatment and rehabilitation), were calculated. Since population at risk has a steady-state given by those who enter -births- and releave it -when they are 15 years old-, if the program did not exist more than 2 million cases and at least 60,000 deaths from measles would have occurred annually. This hypothetical situation is compared with the actual situation of measles in Mexico during the 80's; 1) no more than 100,000 cases could have been estimated to occur in the very extreme case of notifying only one out of 10 cases. 2) The proportions of vaccinated and immune children under five reach 70 percent; this situation has produced 3) a fade out of epidemicity and has increased the critical size of community population for epidemics and doubled the interepidemic interval with the corollary of 4) increasing the average age of infection. The average cost of vaccinating a child was estimated near 1.25 dollars (US). Estimated costs of disease are related to individual losses. Taking into account these factors, benefit/cost ratio of measles immunization in Mexico is, at least, 100:1. Measles transmission patterns in Mexico are discussed since they lead to increase the benefit/cost ratio as compared to countries where the age of infection was put up before the immunization era. To expand investments on measles immunization is recommended.
Assuntos
Sarampo/prevenção & controle , Vacinação/economia , Pré-Escolar , Análise Custo-Benefício , Humanos , Lactente , Sarampo/epidemiologia , Sarampo/mortalidade , México/epidemiologiaRESUMO
A group of 58 children under 4 years old, were vaccinated with trivalent oral poliovirus vaccine Sabin (OPV), in two sanitary areas of Chiapas, Mexico. The complement of procedures for the maintenance of the cold chain, and the changes in the potency of the vaccine prior and after the vaccination were evaluated. Nurses got a blood sample of 3cc and other one, four weeks after vaccination in order to evaluate the seroconversion rate attributable to Sabin vaccine, which was analyzed through neutralization serologic test. Moreover the investigation team got a sample of feces one day prior to vaccination and other one every week in the following three weeks to vaccination date in order to isolate the poliovirus in the feces of the children. The high pre-vaccination seropositivity suggests that in these areas exist a wide circulation of poliovirus, which probably were vaccine viruses and in less proportion wild viruses. The seroconversion rates were low for the three types of poliovirus, nevertheless 83% of the children had at least one of the three possibilities of seroconversion: unique, double or triple. Children with pre-vaccine seropositive probably had a secondary immune response.