According to a study today in Annals of Internal Medicine, fractional dosing of the yellow fever vaccine provides protection for the recipient for up to 10 years without a booster dose.
Results could inform about the use of fractional doses in preventive vaccination campaigns, not just focal conditions. In the related news, Nigeria is vaccinating millions of people after nine people tested positive and Dutch officials reported an imported case of yellow fever.
High levels of seroprotection
The randomized controlled trial was conducted from 2005 to 2007 at Leiden University Medical Center in the Netherlands and included 75 participants who provided blood samples after 10 years of follow-up after receiving a fractional dose of 0.1 ml intradermal or standard 0.5 ml dose subcutaneously.
Participants who received the booster dose during the 10-year 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 out of 75 (97%, 95% confidence interval [CI], 92% to 99%) of subjects had seroprotective antibody levels. Seroprotection was observed in 39 of 40 (98%, 95% CI, 89% to 100%) subjects who received an intradermal fractional dose of 17D-YFV and 34 out of 35 (97%, 95% CI, 87% to 100% who received a subcutaneous standard dose.
Although the fractional dose (one fifth) of the 17D-YFV vaccine has been shown to be non-inferior to full-dose in previous studies, it is the first study to determine long-term immunity. Previously, the authors of this study showed that fractional dose recipients had a protective antibody response in healthy adults 1 year after primary vaccination.
"Our most important finding was that 97% of participants had seroprotective levels of yellow fever neutralizing antibodies 10 years after primary vaccination with one fifth dose of 17D-YFV vaccine," the authors concluded.
Extended use of fractional dose
Fractional dosing has been used in recent years at the outbreak of outbreaks in Brazil and DRC as a way to expand global stockpile of yellow fever vaccine.
In 2006, the World Health Organization (WHO) launched the Yellow Fever initiative, which included preventive mass vaccination campaigns in West Africa and ensured emergency supplies of vaccines. But because the production of the yellow fever vaccine lasts for 12 months and uses embryonated embryonated eggs without pathogens, production is difficult during a major outbreak.
Lead author of MUDr. Anna Roukens of Leiden University Medical Center said the study is an encouraging message for the global vaccine supply.
"If the minimum dose is guaranteed by the manufacturer, there is no reason why the standard dose could not be changed to this effective fractional dose, even in routine vaccinations," said Roukens CIDRAP News.
Nigeria vaccination of 26 million people
In related developments, Nigeria's Center for Disease Control (NCDC) has confirmed more cases of ongoing epidemics in Edo. Since November 21, positive results have been tested for the presence of a virus in nine people.
From September 2017, 140 people positive for the virus were tested in Nigeria. Last week, the ProMed Mail report, an infectious disease information board, 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, which is currently targeting 26.2 million people who have a high level of immunity in this country.
"Vaccination will be for people between the ages of 9 months and 44 years, parents should use themselves and their children to participate in vaccinations, the vaccine is free, safe and effective," said Joseph Oteri, MD, Special Director at the Nigerian National Agency for basic health care.
The campaign will pass on December 1. It is funded by Nigeria, WHO and GAVI, the Alliance.
"Nigeria is primarily in the global battle against yellow fever," said Seth Berkley, MD, CEO of Gavi. "Routine immunization coverage remains dangerously low, as demonstrated by the latest epidemic, and so this campaign is so important for the protection of vulnerable people." While this campaign saves lives, we need to focus on the best long-term solution to routine immunization coverage so that every child is protected, and thus prevent the outbreak in the first place. "
Except for cases in Nigeria, ProMed Mail reports that a Dutch man has a yellow fever after traveling to Gambia and Senegal. He was not vaccinated against the virus and showed signs of liver failure.
November 27 Ann Intern Med studies
November 24 NCDC Press Release
22 WHO Statement Nigeria
Nov 22 ProMed Mail post