Updated
October 1st, 2019

Yellow Fever Vaccine Fractional Dosing Delivered Immunization

Fractional Dose Vaccine Delivered Immunogenicity During a Yellow Fever Outbreak

little boy on beach in yellow clothes

A new study supports the option of using reduced doses of the yellow fever vaccine to meet immunization needs during outbreaks.

These researchers found that the immunologic response to a fractional dose of the 17DD yellow fever vaccine was appropriate for a response to a yellow fever outbreak among children 2 years of age or older and among non-pregnant adults.

In 2016, the world’s yellow fever vaccine stockpile was depleted during the response to two outbreaks. Under the guidance of the World Health Organization (WHO), the local government used 20 percent of the normal dose of the 17DD vaccine, to extend the available supply to meet demand.

The 17DD vaccine, known as Stamaril, was recommended by the WHO for use in this vaccination campaign on the basis of availability, clinical trial data indicating seroresponse to fractional doses, and 5 years of batch-release data.

This study’s finding is important, given the ongoing risk of outbreaks of yellow fever virus.

Because of increased international travel, the yellow fever virus could be on the verge of spreading to various countries. When yellow fever enters an urban cycle the virus’s transmission can spread quickly in overcrowded environments.

As an example, the Centers for Disease Control and Prevention (CDC) have issued a Level 2 Travel Alert for Brazil, a yellow fever hot-zone.

“The extensive outbreak of yellow fever now occurring in Brazil deserves careful attention by world health authorities”, noted Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases.

As such, researchers with the Lancet Infectious Diseases calculated the number of vaccines needed to achieve the 80% population coverage of a full dose as defined by the World Health Organization's (WHO) Global Strategy to Eliminate Yellow Fever Epidemics.

Using the WHO 2016 data sets, these researchers estimate that 383 to 461 million individuals would require vaccinations to achieve the 80% population coverage goal recommended by WHO.

Sanofi is the manufacturer of the 17DD / Stamaril vaccine and says it can meet extended production requirements.

In this study, of 716 people who completed follow-up, 98% had an immune response after vaccination. However, in those who were seropositive at baseline, the percentage who had an immune response after vaccination was lower, at 66%.

Yellow fever is an acute viral disease caused by infection with the yellow fever virus, a flavivirus primarily transmitted to humans through the bite of an infected mosquito, says the CDC.

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Most infected persons are asymptomatic.

However, the case-fatality ratio is 20%–50% among the approximately 15% of infected persons who develop severe disease.

According to the CDC, there is no specific treatment for yellow fever.

Healthcare providers and patients may find locations that can administer STAMARIL vaccine by visiting the CDC web page.

Additionally, providers and patients may also visit the CDC Travelers' Health for information about which countries require yellow fever vaccination for entry.

STAMARIL / 17DD  is considered an investigational vaccine in the USA, as it is not a US-licensed product.

The study was sponsored by the U.S. Agency for International Development and the Centers for Disease Control and Prevention (CDC). The protocol was approved by the medical ethics committee at the University of Kinshasa School of Public Health.

This study was designed and supervised by the authors, who vouch for the accuracy and completeness of the data and analyses and the adherence of the study to the protocol.

The views expressed in this article are those of the authors and do not necessarily represent the official position of the CDC. Fractional vaccine dosing may not meet every patients needs.

These researchers did not report any conflicts of interest: Steve Ahuka-Mundeke, M.D., Ph.D., Rebecca M. Casey, M.B., B.S., M.P.H., Jennifer B. Harris, Ph.D., M.P.H., Meredith G. Dixon, M.D., Pierre M. Nsele, M.D., Gabriel M. Kizito, M.D., Grace Umutesi, M.P.H., Janeen Laven, B.S., Gilson Paluku, M.D., M.P.H., Abdou S. Gueye, M.D., Ph.D., Terri B. Hyde, M.D., M.P.H., Guylain K.M. Sheria, M.D., Ph.D., Jean-Jacques Muyembe-Tanfum, M.D., Ph.D., and J. Erin Staples, M.D., Ph.D.

This article was published on February 14, 2018, at NEJM.org.