1. Institute of Public Health, Department of Community Medicine, Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania
2. Northern Zone Blood Transfusion Centre, P.O. Box 823, Moshi, Tanzania
3. Institute of Public Health, Department of Epidemiology and Biostatistics, Kilimanjaro Christian Medical University College, Moshi, Tanzania
4. Department of Community Medicine, Kilimanjaro Christian Medical Centre, Moshi, Tanzania
5. Department of Pediatrics, Kilimanjaro Christian Centre, Moshi, Tanzania