Measles: the best age and number of doses recommended for children vaccination in Brazil

Abstract

This study was firstly carried out in an adult healthy population, which included university students, blood bank donors and pregnant women with a total of 889 people. It was observed that about 87% of this population carried blood specific measles antibodies, and the same percentage of antibodies detection was observed in each respective newborns, due to the transplacental passage of maternal antibodies. These antibodies were periodically titrated from the day of birth up to 7 months of age. After 4 months of age starts the decline of the antibody levels or its extinction. The response to the vaccine was studied in 1268 children which were divided in 3 groups: I) vaccinated at 7 months and then revaccinated at 15 months; II) vaccinated at 9 months; and III) vaccinated at 7 months and then revaccinated at 9 months. This study have demonstrated that in spite of the response to the vaccine in older children being more efficient, it is very important in the actual epidemiological circumstances of measles in Brazil that the vaccination of children starts at 7 months, despite the percentage of seroconversions being around 50%. This point of view is substantiated by the observation that the mortality index in children under one year of age is responsible for half of the deaths occurring by measles in Brazil. After the second dose of measles vaccine it was not found any difference in the seroconvertion rates in the revaccinated group either at 2 months or 8 months after the first dose of vaccine. The conclusion of this study was the recommendation of the measles vaccine being started at 7 months of age in an attempt to diminish the high mortality and morbidity rates in that group of age, being the revaccination mandatory at 9 months of age in order to protect those children who did not seroconvert after the first dose of vaccine.