Monitoring Efficacy Of Measles Mass Vaccination In Peri-Urban Sites In Khartoum, Sudan

This study was conducted in Mayo, which lies in the South of the capital Khartoum (in the province Gabal Awlia, Elnasr Locality), during the period from July 2001 to June 2002. The main objectives of this study were to evaluate the efficacy of measles mass vaccination in peri-urban sites, to determine the seroconversion rates following measles mass vaccination and to study the clinical susceptibility to measles infection following mass vaccination. A total of 665 children (50.5% males and 49.5% females), aged 9 months to five years were selected using a multistage clustering design. All relevant informations on medical social history, physical examination and anthropometric measurements were noted on a pre-coded questionnaire. Blood samples drawn from a finger prick in special collecting tubes (using painless lancets) were taken from the children before given measles vaccine (i.e. prevaccination samples) and after (i.e. post vaccination sample) vaccination. Analysis of measles specific IgG by Elisa and virus neutralization (VN) tests were done at both home and abroad. The study showed that the predominant age group was 12-23 months and that most of the children belonged to families of low socioeconomic status. The majority of children surveyed showed a positive seroconversion both by ELISA and VN titres (i.e. were above the cut off point of 1.2 OD and 0.3 IU/ml respectively). Seroconversion following mass vaccination was found to be 73% and there were ten cases of measles detected clinically during the three months period of follow up. Sociodemographic factors like, age, breast-feeding, parent’s education and family income did not significantly affect the seroconversion. However, girls had a higher seroconversion rate than boys. Seroconversion did not vary significantly according to the nutritional status nor the current status of health. This study evaluated the primary immune response of the vaccine, further studies were needed to evaluate the secondary immune response of the vaccinated children. It is concluded that mass vaccination is an effective tool in evaluation of measles immune response in the community