The global measles crisis-a diversity of causes from armed conflicts to vaccination skepticism

BACKGROUND AND AIMDespite a safe and effective vaccine being available for many years, the number of measles cases has been increasing again worldwide since 2018. Our report aims to identify putative reasons for this development. METHODSWe conducted a selective literature search. Further, current reports and data from the World Health Organization (WHO), the United Nations Children's Fund (UNICEF), and the World Bank were evaluated. RESULTSAccording to the WHO, Madagascar, the Ukraine, and Israel had the highest incidences of measles worldwide between 1 July 2018 and 30 June 2019. Measles outbreaks are a sign of inadequate vaccination rates caused by multiple structural and psychological barriers. Structural barriers to measles vaccination, such as a lack of routine vaccination programs, have been identified as the main cause of low measles vaccination rates, particularly in fragile countries e.g. due to armed conflicts, but also in some subpopulations of higher-income countries e.g. due to lacking resources for vaccination services. Psychological barriers leading to vaccination skepticism were prevalent mainly in developed countries with well-functioning health systems and a high standard of living. CONCLUSIONThe reasons for the global measles crisis are manifold and in some cases have existed for decades. However, the consequences appear to be accumulating and have had a dramatic impact on case numbers since 2018. The goal of measles elimination and maintenance of the necessary vaccination programs is a constant challenge that requires strict and permanent compliance with WHO recommendations. The number of measles cases reported in Germany is still at a level above the key target for measles elimination specified in the national immunization plan. Timely and/or locally restricted as well as nationwide outbreaks continue to occur. Since infectious agents can be transmitted across borders, the international perspective is an essential component of national health policy in Germany.