Três meses após a campanha de vacinação em massa (cobertura: 100%, faixa etária: 9 meses a 14 anos) contra o sarampo, um inquérito soroepidemiológico foi realizado cm estudantes de um a 19 anos de idade no município de Niterói, estado do Rio de Janeiro. Amostras sangüíneas foram testadas para detecção de anticorpos específicos contra o sarampo por ensaio imunoenzimático (EIE), e os casos negativos testados outra vez utilizando-se a reação de inibição da hemaglutinação (IH) e a neutralização por redução de placas (NP). Das 798 amostras testadas por EIE, 718 (90,2%) foram positivas. A NP foi mais sensível que o EIE e a IH na detecção de anticorpos específicos. A soroprevalência de anticorpos aumentou de 90,2% para 93,2% quando a IH foi empregada em amostras EIE negativas e para 98,9% quando a NP foi utilizada. Após a campanha de vacinação em massa, verificou-se uma diminuição acentuada na incidência do sarampo no município estudado, demonstrando a efetividade da estratégia utilizada para o controle da doença em países em desenvolvimento.

Three months after a mass vaccination campaign (coverage: 100%) against measles a random seroepidemiological survey was carried out in students aged 1 to 19 years old in the Municipality of Niterói, State of Rio de Janeiro. Blood samples were tested for measles antibodies by enzyme immunosorbent assay (EIA) and negative cases were tested again using hemagglutination inhibition (HI) and plaque reduction neutralization (PRN). Of the 798 samples tested by EIA, 718 (90.2%) were positive for measles antibodies. PRN test was more sensitive than EIA and HI in detecting measles specific antibodies. The total antibody prevalence increased from 90.2% to 93.2% when HI was employed in EIA negative specimens and to 98.9% when PRN was used. After the mass vaccination campaign a marked decrease in measles incidence was observed in the municipality studied, showing the effectiveness of the strategy used for measles control in developing countries.

Four virus clones were derived from the Edmonston strain of measles virus by repeated plaque purification. These clones were compared with the vaccine strains Schwarz and CAM-70 in terms of biological activities including plaque formation, hemagglutination, hemolysis and replication in Vero cells and chick embryo fibroblasts (CEF). Two clones of intermediate plaque yielded mixed plaque populations on subcultivation whereas the other two, showing small and large plaque sizes, showed stable plaque phenotypes. The vaccine strains showed consistent homogeneous plaque populations. All the Edmonston clones showed agglutination of monkey erythrocytes in isotonic solution while both vaccine strains hemagglutinated only in the presence of high salt concentrations. Variation in the hemolytic activity was observed among the four clones but no hemolytic activity was detected for the vaccine virus strains. Vaccine strains replicated efficiently both in Vero cells and CEF. All four clones showed efficient replication in Vero cells but different replication profiles in CEF. Two of them replicated efficiently, one was of intermediate efficiency and the other showed no replication in CEF. Two of the clones showed characteristics similar to vaccine strains. One in terms of size and homogeneity of plaques, the other for a low hemolytic activity and both for the efficiency of propagation in CEF.