N. Ishiwada et al., Vaccine-modified measles in previously immunized children in Accra, Ghana:clinical, virological and serological parameters, TR MED I H, 6(9), 2001, pp. 694-698
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.