Soroconversäo da vacina tríplice viral em crianças de 9 e 15 meses de idade / Soroconversion of the MMR vaccine in childrens at 9 and 15 month

A resposta sorológica à vacina tríplice viral foi avaliada em 109 crianças de nove meses de idade, sem história prévia de vacinaçäo contra sarampo, e em 98 crianças de 15 meses de idade, que comprovadamente receberam a vacina monovalente contra o sarampo aos nove meses. A vacina trivalente utilizada continha as seguintes cepas de vírus do sarampo, cepa Urabe Am9 de vírus da caxumba e cepa Wistar RA 27/3 de vírus da rubéola. Um número significantemente maior de crianças do grupo de 15 meses de idade apresentava anticorpos pré-vacinais contra sarampo e caxumba. As taxas de soroconversäo para o sarampo, caxumba e rubéola foram elevadas em ambos os grupos, nä havendo diferenças estatisticamente significantes entre os mesmos. Os títulos de anticorpos pós-vacinais contra a rubéola foram significantemente mais elevados no grupo de crianças de 15 meses de idade. Nenhum evento adverso sério imputável à vacinaçäo foi ibservado.

Immune response to measles, mumps & rubella vaccine at 9, 12 & 15 months of age.

Seroconversion rates to measles, mumps and rubella (MMR) in children given MMR vaccine at 9, 12 and 15 months of age were assessed so as to recommend the optimum age for vaccination. A total of 164 infants were recruited, of whom 123 completed the study. Sera were tested pre-immunization and 4 wk after MMR vaccine, for the presence and titres of antibodies by the haemagglutination inhibition (HI) test and by enzyme-linked immunosorbant assay (ELISA). The pre-immunization results showed that levels of maternal antibody detectable by HI had disappeared by 9 months in all infants in the case of measles, but not in the case of mumps or rubella. Evidence for subclinical infection with the three viruses was found in 19 to 31 per cent of infants by 15 months of age. The responses to measles antigen by both HI test and ELISA were better (> 95%) at 12 or 15 months than at 9 months (80%). Vaccine failure was low at 12 or 15 months. The response to mumps antigen by HI antigen was also higher (92%) at 12 months than at 9 months (75%). Vaccine failure was less frequent at 12 months than at 9 months. The ELISA was found to be unreliable for mumps virus antibody testing. Rubella vaccine evoked good seroresponse (> 92%) at 9, 12 and 15 months, both by HI test and ELISA. Thus a better response to the MMR vaccine was obtained at or after 12 months of age than earlier. Hence, a dose of MMR may be given optimally at 12 months for children not previously immunized with measles vaccine. For those already given measles vaccine, the MMR may be given at 12 or 15 months.