The World Health Organization weekly epidemiological record shows that Nigeria has the highest number of confirmed active cases of Yellow Fever in Africa with about 15-100 confirmed cases.
According to the report, in 2020, 3,426 suspected cases were reported, of which 145 were confirmed either by the regional reference laboratory (RRL) or in-country polymerase chain reaction (PCR). Most confirmed cases were notified from July onwards, in numerous outbreaks, particularly in southern and eastern Nigeria.
Focal outbreaks in rural areas were documented in Bauchi, Benue, Borno, Delta, Ebonyi, and Enugu states from November 2020, although investigations indicated delays in the notification, with probable index cases dating from July 2020 in some states. There was an approximate 20% decrease in the number of suspected cases relative to 2019. The outbreak in some areas of Enugu and Ebonyi necessitated a reactive vaccination campaign in January 2021, targeting approximately 2.75 million people to interrupt transmission.
The campaign was supported by the International Coordinating Group (ICG), a post-campaign coverage survey that showed 74.9% coverage. For the outbreaks in Bauchi, Benue, Borno, and Delta, the country accelerated preventive mass vaccination campaigns (PMVCs) to assure a timely outbreak response. Although challenges were faced in outbreak detection and response, including delays in case notification, stretched resources, limited access due to lack of security, and poor-risk communication, these were addressed by mobilizing national emergency response coordination structures for comprehensive outbreak control, with support from health partners.
Nigeria has the largest number of unvaccinated children, which is why the country is a priority for EYE risk analyses. The EYE strategy has been the key global coordination mechanism of the YF community and has optimized YF control. EYE priorities include increasing vaccination coverage, addressing growing immunity gaps to maintain the gains achieved by mass immunization campaigns during the Yellow Fever Initiative (2006– 2014) in West and Central Africa, and extending the immunity front to high-risk countries.
The country has continued to accelerate campaigns for nationwide protection (target age group, 9 months–44 years). In 2020 and early 2021, PMVCs were conducted for approximately 47.5 million persons in Ekiti and Rivers, which had been postponed from 2019. These were followed by activities in Anambra, Bauchi, Benue, Borno, Delta, Ondo, Osun, and Oyo between October 2020 and February 2021. In Anambra and Oyo, Yellow Fever PMVCs were implemented with dual-antigen vaccine against meningitis in selected age groups, thereby improving campaign efficiency. The PMVCs also served as a form of outbreak response, given the delayed detection of outbreaks described above. The post-campaign coverage survey indicated the following vaccination coverage: Anambra (76.4%), Bauchi (83.4%), Benue (66.9%), Borno (80.1% in 2020; 52.5% in 2021), Delta (75.4%), Ekiti (90.6%), Rivers (82.4%), Ondo (65.8%), Osun (80.0%) and Oyo (75.2%).