**1. Introduction**

Measles is a serious medical problem in Africa, Latin America, Europe, southeast Asia and eastern Mediterranean [1]. During the pre-vaccine era, 130 million measles cases occurred annually worldwide, and it was the leading cause of childhood deaths [2]. In Africa, about 13 million cases and 650,000 deaths occur annually, with sub-Saharan Africa having the highest morbidity and mortality [3]. In 2018, many developing countries reportedly confirmed measles through laboratory testing with high incidence rates. In AFRO region, Liberia confirmed 218 cases with 412.24% incidence rate. Similarly, Libya confirmed 286 cases with 98.84% incidence rate, Burkina Fasso confirmed 567 cases with 84.2% incidence rate and the southern part of the continent was not left out as Uganda confirmed 531 cases in the laboratory with incidence rate of 65.83%. In the Western Pacific region, Philippines confirmed 1677 cases with incidence rate of 118.5% while Malaysia confirmed 1374 cases with incidence rate of 80.35% [4]. In EURO region, Albania confirmed 1290 cases with incidence rate of 477.05%, Georgia reported 1091 laboratory confirmed cases with 374.74% incidence rate and Kyrgyzstan confirmed 376 cases in the laboratory with 75.22% incidence rate. In EMRO, Afghanistan reported 1846 laboratory confirmed cases with 62.64% incidence rate, Saudi Arabia reported 833 laboratory confirmed cases with 29.99% and 793 laboratory confirmed cases in Yemen with incidence rate of 344.36%. Venezuela in AMRO confirmed 5525 cases in the laboratory with an incidence rate of 23.03% [4].

Despite the comprehensive WHO and United Nations International Children Emergency Fund's (UNICEF's) measles-reduction strategy, and partnership of international organizations for measles mortality reduction, certain countries continue to face recurrent epidemics [5]. The optimal age for infantile measles vaccination is an important since maternal antibodies may neutralize the vaccine antigen before specific immune response develops. Delaying vaccination on the other hand may increase risk of complicated disease [6]. Measles vaccine effectiveness is 84% when administered at 9–11 months of age and 93% when given at ≥12 months of age [7]. First dose of measles-containing vaccine (MCV1) given at 9 months of age was introduced into the Expanded Programme on Immunization (EPI) in 1977 [8]. Since >93–95% population immunity is required to prevent measles epidemics, the WHO recommends all children receive two doses of measles vaccine [9]. In Nigeria just like in many developing countries, children are given monovalent measles vaccine at 9 months of age in the EPI [10]. In 2010 and continuing through 2014, DRC experienced the largest nationwide measles outbreak in Africa [11–13]. DRC is a key country for regional elimination efforts because of its large population, central location with nine international borders, and persistent reservoir of circulating measles viruses [14]. The Reaching Every District (RED) approach to strengthening immunization services has been implemented beginning in some developing countries like Democratic Republic of Congo (DRC). A second opportunity for measles vaccination, nationwide measles supplementary immunization activities (SIAs) using a phased approach intended to cover the country every 3 years [15].
