The resurgence of yellow fever outbreaks in Nigeria: a 2-year review 2017–2019

Abstract

Background Yellow fever outbreaks are documented to have a considerable impact not only on the individuals but on the health system with significant economic implications. Efforts to eliminate yellow fever outbreaks globally through the EYE strategy remains important following outbreaks in Africa, Nigeria included. The outbreaks reported in Nigeria, since 2017 and the response efforts provide an opportunity to document and guide interventions for improving future outbreaks in Nigeria and other countries in Africa. Methods We reviewed the available yellow fever surveillance and vaccination response data between September 2017 and September 2019 across the 36 states across Nigeria. We described the epidemiology of the difference outbreaks and the periods for all interventions. We also documented the emergency vaccination responses as well as preventive mass vaccinations implemented towards improving population immunity and limiting epidemic potentials in Nigeria. Results A total of 7894 suspected cases with 287 laboratory-confirmed cases were reported in Nigeria between September 2017 and September 2019 with a mean age of 19 years and a case fatality of 2.7% amongst all reported cases. Outbreaks were confirmed in 55 LGAs with most of the outbreaks across four major epicentres in Kwara/Kogi, Edo, Ebonyi and Bauchi states. In response to these outbreaks, eight reactive vaccination campaigns, supported through ICG applications, were implemented. The duration for responding to the outbreaks ranged from 15 to 132 days (average 68 days) and a total of 45,648,243 persons aged < 45 years vaccinated through reactive and preventive mass campaigns between September 2017 and September 2019. Conclusions Nigeria experienced intermediate outbreaks of yellow fever between September 2017 and 2019 with vaccination responses conducted to control these outbreaks. However, there are delays in the timeliness of responses and more efforts required in improving reporting, response times and preparedness to further prevent morbidity and mortality from the yellow fever disease outbreaks. These efforts, including improving routine yellow fever coverage, contribute towards improving population immunity and other activities related to achieving the goals of the EYE strategy.

Epidemiological profile, trend, seasonality, and factors associated with Yellow fever disease and barriers to vaccination: a retrospective observational study of multi-season national surveillance data in Nigeria, 2017 - 2021

“…Yellow fever (YF), an arthropod-borne, re-emerging viral hemorrhagic illness, caused by the Yellow fever virus (YFV), has remained a significant public health concern in Africa and the Americas, accounting for about 29,000 to 60,000 deaths annually [1][2][3][4][5][6][7][8]. An effective and safe vaccine against YFV, the live attenuated YF 17D vaccine, has been available for over seventy years and integrated into routine immunization (RI) program in endemic countries.…”

“…An effective and safe vaccine against YFV, the live attenuated YF 17D vaccine, has been available for over seventy years and integrated into routine immunization (RI) program in endemic countries. The vaccine has been shown to confer 95% protection in vaccinated populations within 30 days of vaccine uptake and offers life-long immunity [5,6,[9][10][11][12][13]. Infected persons present with a broad spectrum of clinical disease, ranging from asymptomatic infections and mild febrile illness to severe disease and death.…”

Absence of transmission of vYF next generation Yellow Fever vaccine in mosquitoes

“…While urban transmission of yellow fever virus (YFV) can be controlled by public health interventions, the sylvatic cycle is much harder to control given the diversity of wild habitats. Recently, urban outbreaks of YF have been reported in several states in Nigeria [ 8 ] and Brazil [ 9 ]. The YF incidence is estimated to be between 200,000 and 300,000 cases per year.…”

Yellow fever resurgence: An avoidable crisis?

“…The current resurgence of YF is of particular concern as increased population mobility in today’s world amplifies the likelihood of new introductions and resulting local transmission in large population centers near currently affected areas, like Abidjan or Lagos, or to other non-endemic countries with Aedes aegypti populations 27 , 28 . Many areas of the world without YF virus do have Ae.…”

“…Although YF vaccination protects against infection within 7–10 days, implementation of emergency vaccination campaigns to contain rapidly expanding outbreaks is often hampered by limited in-country vaccine supplies, challenges with timely requests to access the emergency stockpile, and problems with vaccine delivery 11 , 27 . In addition, there continue to be competing vaccination priorities (e.g., COVID-19, polio, measles vaccine campaigns) and limitations in YF vaccine supplies as one of the four WHO prequalified manufacturers has paused production during the refurbishing of their facility and a second manufacturer is facing potential supply chain issues.…”