Yellow fever - a tropical acute viral hemorrhagic disease - is a substantial burden that nearly a billion people in the world are currently vulnerable to. This disease is caused by a flavivirus that is transmitted via the bite of infected mosquitos. The name ‘yellow fever’ holds true to symptoms that are commonly associated with those infected which include jaundice, otherwise known as yellowing, of the skin and sclera due to liver damage. Severe cases result in shock, internal bleeding, jaundice and organ failure, and even death.
The infection is currently endemic, meaning always present, in forty-seven countries including Africa (34) and Central and South America (13). In 2013 alone, 127,000 individuals suffered severe infections with 45,000 succumbing to the infection.
More recently in susceptible regions of Brazil, yellow fever has begun to spread through the bite of infected Haemagogus mosquitoes. The outbreak began in mid-2017 and as of January 2018, there have been 35 confirmed cases with 20 reported deaths. As a result, mass vaccination projects supported by the WHO have been launched in Nigeria and Brazil in which the organization plans to vaccinate 25 million people and 24 million people, respectively.
The WHO is deploying nearly 3000 vaccination teams in Nigeria, mainly focused on camps for displaced inhabitants. The vaccination efforts in Brazil are mainly centered around Rio de Janeiro and Sao Paulo where cases of the disease have been prevalent.
Yellow fever is currently preventable through the use of a vaccine that costs between $50 USD to $100 USD. A major roadblock for the mass vaccination initiatives in Nigeria and Brazil is the shortage of yellow fever vaccines available to the public. Even within wealthy countries such as Canada and the United States, the supply of yellow fever vaccines has been temporarily depleted. The vaccine is not recommended for Canadian and US residents unless they are planning to travel to tropical destinations where yellow fever is prevalent. This means that the production of vaccines is not a priority for pharmaceutical companies and thus supplies are not being prepared for mass immunization campaigns like those currently underway.
Good news comes from the fact that during a 2016 yellow fever outbreak in the Democratic Republic of the Congo, supplies of vaccines similarly ran low which forced officials to administer smaller doses of the vaccine to the population. This demonstrated that a lower dose was effective in conferring temporary immunity to the disease which is sufficient in containing outbreaks.
Officials in Brazil and Nigeria have been delivering these fractional doses, which consist of one-fifth of a full vaccine, in order to extend the current supplies and maximize the proportion of the population vaccinated.
A partial dose is effective in providing immunity to the disease for at least twelve months, but the full extent is unknown. Ideally, full doses of the vaccine should be administered as they confer lifelong immunity for 99% of persons vaccinated. Therefore, it is yet to be seen how effective this solution is for immunizing the vulnerable populations. It is critical to vaccinate at least 80% of populations at risk to reduce levels of transmission through herd immunity.
Current initiatives to reduce the prevalence of yellow fever include the Eliminate Yellow fever Epidemics (EYE) Strategy which was launched in 2017. With the collaboration of more than 50 partners, the EYE partnership supports at-risk countries in Africa and the Americas to prevent, detect, and respond to yellow fever suspected cases and outbreaks. By 2026, it is expected that over 1 billion people will be protected against the disease and strategies will be developed to prevent international spread and contain outbreaks rapidly.
We, as university students, have a role to play in bridging the gap in access to essential medicines such as the yellow fever vaccine. Due to the current shortage in Brazil, this vaccine remains out of reach for many vulnerable populations. Life-saving vaccines should not be a luxury. Let's address the drug availability problem by advocating for and developing initiatives that allow all of those at risk to have access to the vaccines they need.
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Written by: Ethan McQueen and Michael Bridgeraj
Ethan and Michael are currently in their second year of undergraduate studies at Western University. Ethan serves as a UAEM Access Representative and Michael serves as an UAEM Innovation Representative.