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Partial-dose Yellow Fever Vaccine Effective in Emergencies


27 February, 2018

A new study suggests that partial doses of the yellow fever vaccine can help protect communities against the disease.

The study was published in the New England Journal of Medicine. It found that individuals given a one-fifth dose of yellow fever vaccine developed enough antibodies to protect them against infection.

Erin Staples was one of the writers of a report on the study. She says this is good news in places where the vaccine is in short supply.

A boy cries as he receives a vaccine against yellow fever at a public health center in Sao Paulo, Brazil, Jan. 16, 2018.
A boy cries as he receives a vaccine against yellow fever at a public health center in Sao Paulo, Brazil, Jan. 16, 2018.

"That was the encouraging thing, that this can be done as a potential way — when there's supply limitations on the vaccine — to help potentially control an outbreak."

Staples works for the Centers for Disease Control and Prevention (CDC), which is an agency of the United States government.

Yellow fever is a serious problem in parts of Africa, as well as Central and South America. People get the disease from infected mosquitoes. The term "yellow" in the name describes the yellow coloring of some patients' skin.

The World Health Organization says a small number of patients develop severe health problems and about half of them die within seven to 10 days.

Staples noted that in the Democratic Republic of the Congo, health workers had to use partial doses of the yellow fever vaccine in 2016. At that time, the vaccine was in short supply.

The World Health Organization suggested a one-fifth dose based on some experiments performed in Brazil. Staples said many experts wondered if a partial dosage would be effective against the disease. She noted that nearly 8 million people were targeted for vaccination in the city of Kinshasa.

"It worked in small cohorts, in a well-controlled clinical trial situation. But when you go to do this large scale in the field, does it work?"

The partial amount proved effective. Ninety-eight percent of people tested had protective antibodies to the virus one month after being vaccinated.

In Brazil, more than 350 people have become sick with yellow fever since late last year. Vaccine supplies remain in short supply.

Health officials have launched what they are calling the largest-ever partial-dose mass vaccination campaign. The goal is to vaccinate nearly 24 million people. Each person is being given a one-fifth dose of the yellow fever vaccine.

Staples says the new research offers hope.

"I think that's very encouraging for the short term, immediate control. We still need some information about how long immunity will last."

A full dose of yellow fever vaccine provides lifelong protection against the disease. Researchers will continue to study how long people who received partial doses are protected.

I'm Jonathan Evans.

Steve Baragona reported this story for VOA News. Jonathan Evans adapted his report for VOA Learning English. George Grow was the editor.

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Words in this Story

antibody n. a substance produced by the body to fight disease

dose n. the amount of a medicine, drug, or vitamin that is taken at one time

encouraging – adj. causing a hopeful feeling

outbreakn. a sudden increase in the number of cases of a disease

cohort – n. a friend or someone you know

clinicaladj. related to a place where medical treatment is provided

scale – n. the size of something, especially when compared to something else

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