Vaccine-modified measles in previously immunized children in Accra, Ghana:clinical, virological and serological parameters

Despite rapidly increasing measles immunization coverage, epidemics of meas les occurred from January to March 2000 in some parts of Accra, the capital of Ghana. 44 cases of acute measles were diagnosed at three health facilit ies during the outbreaks, which we examined clinically and serologically. T he peak incidence occurred among 6-12-year-olds, clinical symptoms were mil der than the typical symptoms of measles, and fever was significantly less common. None of the cases developed complications and all recovered complet ely. Thirty-eight (86.4%) were tested serologically; IgM antibodies were de tected in 73.7% and IgG antibodies in 84.2% during the acute phase. Milder symptoms in a significant number of cases with measles IgG antibodies sugge st that these are vaccine-modified measles, attributable to waning antibodi es and low circulation of wild type virus in an area of high vaccine covera ge. Serological confirmation will be required for accurate diagnosis, if me asles is to be eradicated or kept under control. It also seems likely that multiple dose immunization schedules will be needed in the future to mainta in protective antibody levels and to protect children against measles in Gh ana. This will eliminate the frequent outbreaks of measles involving immuni zed children.