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Study claims fractional dosing with yellow fever vaccine

According to a study carried out today in the Annals of Internal Medicine, The fractionated dose of the yellow fever vaccine offers the receptors protective antibodies for up to 10 years without a booster dose.

The results could inform the use of fractionated dose in preventive vaccination campaigns, and not only the configuration of outbreaks. In related news, Nigeria is vaccinating millions of people after nine people recently obtained a positive result, and the Dutch authorities report on an imported case of yellow fever.

High levels of seroprotection.

The randomized controlled trial was conducted between 2005 and 2007 at Leiden University Medical Center in the Netherlands and included 75 participants who provided blood samples at 10 years of follow-up after receiving a fractional dose of 0.1 milliliter (mL) of the intradermal vaccine or The standard dose of 0.5 ml subcutaneously.

Participants who received a booster dose during 10 years of follow-up were excluded from the study. Both groups received the same vaccine, manufactured by Sanofi Pasteur.

According to the authors, 10 years after primary vaccination, 73 of 75 (97%, 95% confidence interval) [CI], 92% to 99%) participants had seroprotective antibody levels. Seroprotection was observed in 39 of 40 (98%, 95% CI, 89% to 100%) participants who received the fractional intradermal dose of the 17D-YFV vaccine and 34 of 35 (97%, 95% CI, 87 % to 100%). ) who received the standard subcutaneous dose.

Although the fractional dose (one fifth) of the 17D-YFV vaccine has been shown to be not inferior to full doses in previous studies, this is the first study to establish long-term immunity. Previously, the authors of this study showed that recipients of the fractional dose showed a protective antibody response in healthy adults one year after primary vaccination.

"Our most important finding was that 97% of the participants had seroprotective levels of neutralizing antibodies to yellow fever 10 years after primary vaccination with a fifth dose of the 17D-YFV vaccine," the authors concluded.

Extension of the use of fractional dosing.

The fractional dose has been used in recent years in outbreaks in Brazil and the Democratic Republic of the Congo (DRC) as a way to stretch the world reserves of yellow fever vaccine.

In 2006, the World Health Organization (WHO) started the Yellow Fever Initiative, which involved massive preventive vaccination campaigns in West Africa and secured a reserve of emergency vaccines. But since the production of the yellow fever vaccine takes 12 months and uses pathogen-free embryonated eggs, production is difficult during a major outbreak.

The study's lead author, Anna Roukens, MD, PhD, of the Leiden University Medical Center, said the study was encouraging news for the world's vaccine stockpile.

"If the manufacturer guarantees the minimum dose, there is no reason why the standard dose can not be changed at this effective fractional dose, even in routine vaccines," Roukens told CIDRAP News.

Nigeria vaccinating 26 million people.

In related developments, the Center for Disease Control of Nigeria (NCDC) confirmed more cases in an ongoing outbreak in the state of Edo. Until November 21, nine people tested positive for the virus.

Since September 2017, 140 people in Nigeria have tested positive for the virus. Last week, ProMed Mail, a panel of infectious disease messages, said two people in Edo probably died of yellow fever.

Nigeria is in the middle of the second phase of the largest vaccination campaign against yellow fever in history, which aims to reach 26.2 million people to establish a high level of immunity in that country.

"Vaccination will be for people within the cohort from 9 months to 44 years, it is recommended that parents use them and their children to participate in the vaccination, the vaccine is free, safe and effective," said Joseph Oteri, MD, director of special duties at the National Agency for Development of Primary Health Care of Nigeria.

The campaign will be held until December 1. It is funded by Nigeria, WHO and GAVI, the Vaccine Alliance.

"Nigeria is on the front line in the global battle against yellow fever," said Seth Berkley, MD, CEO of Gavi. "Routine immunization coverage remains dangerously low, as evidenced by the latest outbreak, which is why this campaign is so important to protect the vulnerable." While this campaign will save lives, we must focus our efforts on the best solution to long-term: improve "routine immunization coverage so that all children are protected, preventing outbreaks from occurring in the first place".

In addition to the cases in Nigeria, ProMed Mail notes that a Dutchman has yellow fever after traveling to Gambia and Senegal. He was not vaccinated against the virus and shows signs of liver failure.

See also:

Nov 27 Ann Intern Med study

November 24 press release from NCDC

November 22 statement from the WHO office in Nigeria

Nov 22 ProMed Mail post

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