Children May Need 2-Doses Of Yellow Fever Vaccine
A new study on the effectiveness of the Yellow Fever virus vaccine indicates the current dosage schedule may not be protecting children over the long term.
This study published in The Lancet on September 19, 2019, showed a large decline in humoral immunity to yellow fever after 2–6 years in each group of children in this study.
These researchers found the proportions of seropositive children approximately halved, leaving large proportions of the study populations with negative serostatus.
This is important news since some countries are reporting Yellow Fever case fatality ratios over 30 percent.
‘The long-term decline of humoral immunity suggests that a single dose of the vaccine, administered at 9 months of age, might not achieve a population immunity protective against yellow fever epidemics.’
‘Our findings argue for the 1-dose-for-life guidelines to be reconsidered for individuals who receive yellow fever vaccination as infants,’ said these researchers.
This is important news since Yellow fever is an expanding concern in 34 African countries and 13 countries in the Americas.
It is estimated that about 400 million people will require vaccination to achieve the population immunity recommended by the World Health Organization (WHO) for countries at risk.
Since 2013, the WHO has recommended a single dose of yellow fever vaccine for life-long immunity, and the amended International Health Regulations (2005) no longer require revaccination every 10 years.
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The current vaccines against yellow fever, such as YF-Vax and Stamaril, are safe and efficacious and consist of live attenuated virus that is usually administered by subcutaneous injection, said these researchers.
The WHO’s current guidelines advocate a single dose of vaccine for life-long protective immunity against yellow fever. In endemic countries, the vaccine is routinely given to infants at 9–12 months of age as part of the WHO Expanded Programme on Immunization.
Several previous studies have shown a decrease in seropositivity and antibody titers over time, with 71–82 percent of adults seropositive 10 years or more after vaccination.
Children, however, showed lower seroconversion rates and titers than healthy adults and might lose immunity faster.
Yellow fever is an acute viral hemorrhagic disease transmitted by infected mosquitoes, says the WHO.
The Yellow fever virus is an RNA virus that belongs to the genus Flavivirus. It is related to West Nile, St. Louis encephalitis, and Japanese encephalitis viruses.
There is no medicine to treat or cure the infection of a yellow fever infection. Symptoms include fever, headache, jaundice, muscle pain, nausea, vomiting, and fatigue. Rest, drink fluids, and use pain relievers and medication to reduce fever and relieve aching, says the WHO.
To alert USA-based international travelers, the Centers for Disease Control and Prevention (CDC) updated its vaccination information during May 2019.
The CDC says a single dose provides lifelong protection for most people. And, the CDC recommends vaccination for people aged 9 months or older and who are traveling to or living in areas at risk for yellow fever virus, such as Africa and South America.
According to the CDC, the Yellow fever vaccine availability in the United States is currently limited. If you need to be vaccinated before an international trip, you may need to schedule an appointment well in advance.
During 2019, the Stamaril vaccine should be administered at least 10 days before entering an endemic area for the protective immunity to be achieved.
Sanofi Pasteur, the manufacturer of the only yellow fever vaccine YF-Vax licensed in the United States, expects to provide an update by the end of 2019 on the return to the supply of YF-Vax, says the CDC.
Additionally, some countries require international travelers to present proof of yellow fever vaccination upon arrival.
Unfortunately, fake ‘yellow-cards’ have been reported in Africa.
During July 2019, a report published in The Lancet discussed how it is possible to obtain a government-issued Yellow Fever vaccination certificate in Nigeria, without actually getting the Stamaril vaccine.
“Contravention of the International Certificate of Vaccination or Prophylaxis (ICVP) comes in various forms,” Oyewale Tomori, professor of virology and former vice-chancellor of Redeemer's University in Ogun State, Nigeria, told The Lancet.
The ICVP as described by the WHO International Health Regulations (IHR) 2005 and often called the Yellow Card, has long been accepted as evidence of a traveler's vaccination status.
Note: The CDC says any vaccine can cause side effects, which should be reported to a healthcare provider or to the CDC.
Yellow Fever vaccine news published by Vax-Before-Travel