Sunday February 17, 2019

Study: Partial Dose of Yellow Fever Vaccine Provides Protection

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

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Yellow fever is a mosquito-borne viral disease found in tropical Africa and South and Central America.
Yellow fever is a mosquito-borne viral disease found in tropical Africa and South and Central America. Wikimedia Commons
  • Yellow fever is a mosquito-borne viral disease
  • Severe cases can cause jaundice and death, but most cases involve fever, muscle pain and vomiting
  • More than 350 people have become infected with yellow fever in Brazil since late last year

When stockpiles of yellow fever vaccine run low, partial doses are effective, according to a new study.

The report on the vaccine, which currently is in short supply, comes as officials in Brazil attempt to contain an outbreak with what they describe as the largest-ever mass vaccination campaign using partial doses.

Yellow fever is a mosquito-borne viral disease found in tropical Africa and South and Central America. Severe cases can cause jaundice and death, but most cases involve fever, muscle pain and vomiting.

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Congo outbreak, experiment

During a major outbreak in the Democratic Republic of the Congo in 2016, the government aimed to prevent the disease from spreading in the capital, Kinshasa. Health officials launched a mass vaccination campaign targeting 7.6 million people.

But the outbreak had depleted vaccine stockpiles. Hoping to stretch the available supply, the World Health Organization reviewed the small number of available studies on using reduced doses and recommended using one-fifth of a dose per person.

It seemed to work.

Health officials have launched a campaign targeting nearly 24 million people with a one-fifth dose of the vaccine. Wikimedia Commons
Health officials have launched a campaign targeting nearly 24 million people with a one-fifth dose of the vaccine. Wikimedia Commons

Researchers took blood samples from more than 700 people before and after they received the partial dose. In the new study, published in the New England Journal of Medicine, nearly all of those vaccinated with the lower dose developed enough antibodies to the virus to prevent infection.

“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,” said study co-author Erin Staples at the U.S. Centers for Disease Control and Prevention.

Hundreds infected

More than 350 people have become infected with yellow fever in Brazil since late last year, and health officials have launched a campaign targeting nearly 24 million people with a one-fifth dose of the vaccine.

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Staples says the new study is good news for controlling outbreaks like Brazil’s in the short term. But, she notes, “We still need some information about how long immunity will last.”

A full dose of yellow fever vaccine provides lifelong immunity. Researchers will continue to study how long people who received partial doses are protected. (VOA)

Next Story

WHO Makes Progress In Controlling Ebola In Congo

In addition, 2,600 health care workers in Uganda have been vaccinated.

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Ebola, COngo
Health workers treat an unconfirmed Ebola patient inside a MSF (Doctors Without Borders)-supported Ebola Treatment Center (ETC) in Butembo, Democratic Republic of Congo, Nov. 3, 2018. VOA

Six months after the outbreak of Ebola was declared in the Democratic Republic of Congo’s North Kivu province, the World Health Organization is expressing cautious optimism that it is making headway in controlling the spread of the deadly virus.

Latest figures reported by the WHO show 752 cases of Ebola, including 465 deaths.

WHO Regional Director for Africa, Matshidiso Moeti, says progress in containing the spread of the virus is due to a number of public health measures, including the training of health workers on infection prevention and control, closer engagement with communities, case investigation and contact tracing.

Ebola
Medical staff are sterilized before entering the isolation unit at a hospital in Bundibugyo, western Uganda, on Aug. 17, 2018, where there is one suspected case of Ebola. VOA

She says the use of a vaccine and promising new drugs have been a boon to these efforts.

“I feel optimistic,” Moeti said. “I am very clear that we need to continue this work. We need to make sure that in the places where we have made progress, we build on this progress and we do not go back. And, we are being very, very conscious of the fact that we need to invest to improve the preparedness both in the DRC areas that are highest at risk and, most importantly, in the surrounding countries that are at risk.”

Ebola, mother
Medecins Sans Frontieres (MSF) workers talk to a worker at an isolation facility, prepared to receive suspected Ebola cases, at the Mbandaka General Hospital, in Mbandaka, Democratic Republic of Congo, May 20, 2018. VOA

The risk of the virus spreading to countries like Uganda, Rwanda and South Sudan is very high because of the heavy cross-border traffic among the countries, Moeti said. However, she added, surveillance and preparedness activities have been enhanced on both sides of the border.

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She says there is extensive monitoring at border crossings and improvements have been made in screening people for the virus. In addition, 2,600 health care workers in Uganda have been vaccinated. Moeti said a similar vaccination campaign began two days ago in South Sudan. (VOA)