Nigeria: One-Fifth of Yellow Fever Vaccine Very Effective - Study

Yellow fever signs and symptoms.
14 January 2021

According to the study, giving a person one-fifth of the vaccine dose is safe.

The administering of a fraction of the standard yellow fever vaccine is effective and could help vaccinate millions of people during emergencies, a new study has shown.

The study led by the research arm of Doctors Without Borders/Médecins Sans Frontiéres' (MSF), Epicentre, and published in The Lancet shows that fractioning doses of the yellow fever vaccine is effective and safe.

According to the study, giving a person one-fifth of the vaccine dose is safe and could prevent people from getting sick from the disease.

"These clinical trial results found that giving a person one-fifth of the standard yellow fever vaccine dose is effective and safe," MSF said in a statement published on its website.

It said this will make it easier for governments and international organizations to prevent people from getting sick from yellow fever during outbreaks in times of vaccine shortage.

"When big yellow fever epidemics hit, countries and MSF need to access vaccines urgently."

"This study means that treatment providers can now rest assured that giving people smaller doses of any of the World Health Organization (WHO) prequalified yellow fever vaccines will protect the person in front of them while helping to keep even more people safe," Myriam Henkens, MSF international medical coordinator, said.

Yellow fever

Yellow fever is an acute viral hemorrhagic fever that causes 30,000 deaths per year, most of which occur in Sub-Saharan Africa. However, the disease is on the rise in Central and South America.

While this infection is asymptomatic or causes only mild symptoms in many people, a small percentage of those infected experience a more toxic stage of the disease that can cause internal bleeding and severe damage to the liver and kidneys.

Approximately half the people who enter this stage of yellow fever die within a few days.

There's no cure for yellow fever, so prevention is extremely important. A single dose of the vaccine can protect a person for life.

Yellow fever is endemic to 34 countries in Africa, including Nigeria.

According to the latest Nigeria Centre for Disease Control (NCDC) Yellow Fever situation report, from January 1 to December 25, cases were reported in 13 states including Akwa Ibom, Bauchi, Benue, Borno, Delta, Ebonyi, Enugu, Gombe, Kogi, Osun, Oyo, Plateau and Taraba.

A total of 3,112 suspected cases and 109 confirmed cases were reported from 30 LGAs in the 13 states. A total of 17 deaths was recorded among the confirmed cases with a (Case Fatality Rate) CFR of 17 per cent from Enugu (9), Delta (6), Bauchi (1) and Ebonyi (1).

Meanwhile, there were 249 deaths overall from suspected yellow fever infections, the highest yearly tally since the resurgence of the disease in 2017.

The Yellow Fever vaccination was introduced in Nigeria in 2004 as one of the routine vaccines expected to be given to children during routine immunisation. In spite of this, the country is still witnessing outbreaks of the disease.

The increasingly regular occurrence of outbreaks is largely because many people are not immunised, according to the NCDC. Vaccine hesitancy -- a reluctance or refusal to be immunised -- was named by the World Health Organisation as one of the top 10 threats to global health in 2019.


The Epicentre study, in collaboration with the Kenya Medical Research Institute, Institut Pasteur de Dakar, and the WHO, was a randomized, double-blind trial in Mbarara, Uganda and Kilifi, Kenya conducted between November 6, 2017, and February 21, 2018.

During this period, researchers administered either one-fifth or a standard dose of yellow fever vaccine to 960 adults between the ages of 18 and 59 years old.

People receiving one-fifth of the dose were found to have an immunological response that was considered non-inferior to the standard dose.

"This is an important step toward a future updated policy on fractional doses. Thanks to these results, the current WHO policy on fractional doses of yellow fever vaccines in times of shortages during an outbreak can be expanded to all prequalified vaccines," the statement reads.

According to MSF, this clinical trial marks the first time all four WHO prequalified yellow fever vaccines have been assessed in the same study.

The study used the only four existing WHO-approved vaccines, which are derived from multiple strains of the virus: 17DD (Bio-Manguinhos/Fiocruz, Brazil), 17D-213 (Federal State Unitary Enterprise of Chumakov Institut of Poliomyelitis and Viral Encephalitides, Russia), 17D-204 (Institut Pasteur de Dakar, Senegal), and 17D-204 (Sanofi Pasteur, France).

"This research is significant because it shows that trials involving different manufacturers, where their products are independently evaluated, is possible," said Rebecca Grais, research director of MSF's Epicentre.

"This is proof that global medical researchers can band together to do independent and objective research that results in products and recommendations that truly meet the needs of people and ensure effective and safe medicines and vaccines."

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