JSI Research and Training Institute, Inc. Innovative learning strategies outside of formal classroom trainings are needed to improve frontline health workers competencies for achieving immunization coverage goals that have become more important now during the COVID-19 pandemic. Immunisation training for healthcare providers has until recently predominately taken the form of classroom-based lectures. Increasingly, however, learner-centred education methods are being used to encourage active participation and learning, with the traditional lecture method complemented by need-based, individualised, and interactive immunisation capacity building that doesn t disrupt healthcare workers regular duties and that strengthens networking and communication among nurses. This case study describes JSI (John Snow, Inc.) Research & Training Institute s pilot use of peer mentoring with WhatsApp for immunisation capacity building of maternal and child health (MCH) nurses in the Lari and Machako