1. Institute of Public Health, Department of Community Medicine, Kilimanjaro Christian Medical University College (KCMUCo), P.O. Box 2240, Moshi, Tanzania
2. Institute of Public Health, Department of Epidemiology and Biostatistics, KCMUCo, Moshi, Tanzania
3. Northern Zone Blood Transfusion Centre, P.O. Box 823, Moshi, Tanzania
4. Department of Pediatrics, Kilimanjaro Christian Medical Centre (KCMC), Box 3010, Moshi, Tanzania
5. Department of Community Medicine, Kilimanjaro Christian Medical Centre (KCMC), Moshi, Tanzania