BackgroundIn the occupied Palestinian territory, the expanded programme on immunisation (EPI) has successfully targeted 13 diseases through vaccination and achieved high population coverage. However, surveillance of adverse events following immunisation (AEFI) is inadequate in the Gaza Strip, as only post-BCG lymphadenitis is reported. This study assessed the adherence of health-care workers (HCWs) to the AEFI surveillance system in the Gaza Strip. MethodsData were collected by four methods: 105 HCWs answered a questionnaire; 24 health facilities completed a checklist enquiry; 17 medical health officers and information system managers from Ministry of Health (MOH) and UNRWA health centres and hospitals underwent in-depth interviews; and a focus group was held with 22 epidemiologists, stakeholders, consultants, and managers of the EPI. The 24 health facilities comprised seven MOH primary health-care centres (PHCs) providing vaccination, five MOH PHCs not providing vaccination, seven UNRWA PHCs, and the five hospitals of the Gaza Strip with paediatric departments. Data collected from June, 2015, to August, 2015, were analysed with SPSS version 19. Relationships among variables were assessed by independent t tests, chi squared tests and one-way ANOVA. Verbal informed consent was obtained from all participants, and written approval for the study was obtained from MOH and UNWRA directorates. FindingsAEFI are reported infrequently; approximately half of the 105 HCWs (51%; 53) report AEFI, but there were conflicting views as to whom they should report. 65% (68) thought that they should report all AEFI. Participants’ educational background, participation in workshops, and number of years of employment affected AEFI recognition and reporting. The majority (74%; 78) participate in immunisation workshops. There is an ineffective structure in MOH centres, and the UNRWA has a well-established internal system for reporting AEFI but a poor system for external reporting to the MOH epidemiology department. A lack of HCW awareness of responsibilities may also have a role. The majority of HCWs (95%; 100) reported a need for further training, and all reported a lack of cooperation or coordination between hospitals and PHCs regarding AEFI notification. All individuals (17) who were interviewed knew that they must report AEFI. A majority (65%; 11) stated no difficulties, whereas some (35%; six) reported difficulties due to absence of guidelines, protocols, or notification forms, and to fear of punishment. Focus group participants felt that all AEFI should be reported. They agreed that HCWs face obstacles such as fear of consequences, lack of knowledge and training, high workloads, not considering AEFI as related to immunisation, and absence or shortage of notification forms, protocols, and guidelines. Some felt that certain AEFI should be reported only to treating doctors, but all agreed that there is no cooperation or coordination among PHCs and between hospitals and PHCs regarding AEFI reporting. InterpretationCommon themes may explain poor adherence of HCWs to AEFI surveillance. The system is ineffective in MOH centres, and UNRWA PHCs have well-established internal but poor external reporting systems. Absence of monitoring may have a role, and a lack of guidelines, protocols, and forms for reporting were mentioned by HCWs, medical health officers and information system managers, and the focus group. Some HCWs may not know their responsibilities (eg, to whom AEFI should be reported). Many other obstacles face HCWs, including fear of punishment and accountability. Therefore, HCWs must be encouraged to report adverse events without fear of penalty. In addition, lack of education on AEFI and lack of experience in identifying AEFI may affect reporting. Training of HCWs, development of guidelines and protocols, database construction and design, and monitoring of the AEFI surveillance system are highly recommended. FundingWHO EMRO.