The Nigerian government with support from the World Health Organisation (WHO) and partners will today launch a mass vaccination campaign to prevent the spread of yellow fever in the country.
According to WHO, more than 25 million people will be vaccinated throughout 2018 in the planned campaign, which it declared is going to be the largest yellow fever vaccination drive in the country’s history.
The organisation revealed that the immunisation plan is part of efforts to eliminate yellow fever epidemics globally by 2026. The preventive campaign it said, will use vaccines funded by Gavi, the Vaccine Alliance, and will be supported by United Nations Children’s Fund (UNICEF).
Executive Director of National Primary Healthcare Development Agency, Dr. Faisal Shuaib, said the exercise will commence today in Kogi, Kwara and Zamfara states, and then move to Borno state where it will focus on camps for internally displaced persons and surrounding host communities.
“More than 8.6 million people will be vaccinated in the four states in the coming days. The goal of the Yellow Fever Preventive Mass Vaccination Campaign is to reduce yellow fever transmission by achieving 90 per cent coverage in implementing states and local government areas in line with the strategy for the elimination of yellow fever epidemics by 2026,” Shuaib said.
Yellow fever as stated by WHO, is a vaccine-preventable acute viral haemorrhagic disease transmitted by infected mosquitoes. The current yellow fever outbreak in Nigeria began in Ifelodun, Kwara State in western Nigeria in September 2017. By early January 2018, a total of 358 suspected cases had been reported in 16 states, with 45 deaths.
“In late 2017, Nigeria vaccinated more than three million people in an initial emergency yellow fever vaccination campaign with the aim of quickly containing the outbreak. However, the yellow fever virus continues to circulate in different parts of the country where people remain largely unprotected.”
WHO representative in Nigeria, Dr. Wondimagegnehu Alemu, said the organisation is supporting the vaccine drive by training thousands of healthcare workers on how to administer the vaccine; helping to track cases of yellow fever and providing coordination and logistical support for the highly complex operation.
“With a single dose of vaccine, an individual is protected for life against yellow fever. This is a massive undertaking which took weeks of planning. Nearly 3000 vaccination teams are being deployed across the four states participating in the campaign,” Alemu said.
He added that a coalition of partners developed the Eliminate Yellow fever Epidemics (EYE) Strategy, steered by WHO, Gavi and UNICEF, to protect at-risk populations, prevent international spread and contain outbreaks rapidly. As a zoonosis (any disease or infection that is naturally transmissible from vertebrate animals to humans), yellow fever cannot be eradicated, but epidemics can be eliminated if population immunity levels are effectively raised through mass vaccination and sustained by routine infant immunization.
The EYE Strategy’s goal is to eliminate yellow fever epidemics globally by 2026. A second phase of the mass vaccination campaign in Nigeria, he disclosed is expected to occur later in 2018. This is part of a phased approach to build immunity among residents.
“This should provide high population immunity nationwide. WHO calls for partners’ continued support to protect the Nigerian people and end yellow fever epidemics by 2026,” Dr Alemu said.
Key facts as documented by WHO, reveal that yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. The “yellow” in the name refers to the jaundice that affects some patients.
Symptoms of yellow fever include fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue.
A small proportion of patients who contract the virus develop severe symptoms and approximately half of those die within seven to 10 days.
The virus is endemic in tropical areas of Africa and Central and South America.
Since the launch of the Yellow Fever Initiative in 2006, significant progress in combatting the disease has been made in West Africa and more than 105 million people have been vaccinated in mass campaigns. No outbreaks of yellow fever were reported in West Africa during 2015.
Large epidemics of yellow fever occur when infected people introduce the virus into heavily populated areas with high mosquito density and where most people have little or no immunity, due to lack of vaccination. In these conditions, infected mosquitoes transmit the virus from person to person.
Yellow fever is prevented by an extremely effective vaccine, which is safe and affordable. A single dose of yellow fever vaccine is sufficient to confer sustained immunity and life-long protection against yellow fever disease and a booster dose of the vaccine is not needed. The vaccine provides effective immunity within 30 days for 99 per cent of persons vaccinated. Good supportive treatment in hospitals improves survival rates. There is currently no specific anti-viral drug for yellow fever.
On signs and symptoms: once contracted, the yellow fever virus incubates in the body for three to six days. Many people do not experience symptoms, but when these do occur, the most common are fever, muscle pain with prominent backache, headache, loss of appetite, and nausea or vomiting. In most cases, symptoms disappear after three to four days.
A small percentage of patients, however, enter a second, more toxic phase within 24 hours of recovering from initial symptoms. High fever returns and several body systems are affected, usually the liver and the kidneys. In this phase people are likely to develop jaundice (yellowing of the skin and eyes, hence the name ‘yellow fever’), dark urine and abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes or stomach. Half of the patients who enter the toxic phase die within seven to 10 days.
Yellow fever is difficult to diagnose, especially during the early stages. More severe disease can be confused with severe malaria, leptospirosis, viral hepatitis (especially fulminant forms), other haemorrhagic fevers, infection with other flaviviruses (e.g. dengue haemorrhagic fever), and poisoning.
Blood tests (RT-PCR) can sometimes detect the virus in the early stages of the disease. In later stages of the disease, testing to identify antibodies is needed (ELISA and PRNT).
On transmission: The yellow fever virus is an arbovirus of the flavivirus genus and is transmitted by mosquitoes, belonging to the Aedes and Haemogogus species. The different mosquito species live in different habitats – some breed around houses (domestic), others in the jungle (wild), and some in both habitats (semi-domestic). There are three types of transmission cycles. They are sylvatic (or jungle) yellow fever; intermediate yellow fever; and urban yellow fever.
On the issue of treatment, the WHO document further revealed that good and early supportive treatment in hospitals improves survival rates. There is currently no specific anti-viral drug for yellow fever but specific care to treat dehydration, liver and kidney failure, and fever improves outcomes. Associated bacterial infections can be treated with antibiotics.
The document also showed that vaccination is the most important means of preventing yellow fever. In high-risk areas where vaccination coverage is low, prompt recognition and control of outbreaks using mass immunisation is critical for preventing epidemics.
Others are mosquito control and epidemic preparedness and response. The risk of yellow fever transmission in urban areas can be reduced by eliminating potential mosquito breeding sites by applying larvicides to water storage containers and other places where standing water collects.
Insecticide spraying to kill adult mosquitoes during urban epidemics can help reduce the number of mosquitoes, thus reducing potential sources of yellow fever transmission.
Historically, mosquito control campaigns successfully eliminated Aedes aegypti, the urban yellow fever vector, from most of Central and South America. However, Aedes aegypti has re-colonized urban areas in the region, raising a renewed risk of urban yellow fever. Mosquito control programmes targeting wild mosquitoes in forested areas are not practical for preventing jungle (or sylvatic) yellow fever transmission.
On epidemic preparedness and response, it stated that prompt detection of yellow fever and rapid response through emergency vaccination campaigns are essential for controlling outbreaks. However, underreporting is a concern. The true number of cases is estimated to be 10 to 250 times what is now being reported.
WHO recommends that every at-risk country have at least one national laboratory where basic yellow fever blood tests can be performed. One laboratory-confirmed case of yellow fever in an unvaccinated population is considered an outbreak. A confirmed case in any context must be fully investigated, particularly in an area where most of the population has been vaccinated. Investigation teams must assess and respond to the outbreak with both emergency measures and longer-term immunisation plans.
