YF-VAX® Yellow Fever Vaccine Clinical Trials, Dosage, Efficacy, Side Effects
Sanofi Pasteur YF-VAX® vaccine is prepared by culturing the 17D-204 strain of yellow fever virus in living avian leukosis-free chicken embryos. YF-Vax contains sorbitol and gelatin as stabilizers, is lyophilized, and is hermetically sealed under nitrogen, and no preservative is added. The YF-VAX vaccine must be reconstituted immediately before using the sterile diluent provided (Sodium Chloride Injection USP). After reconstitution, YF-VAX is a slightly pink-brown suspension that complies with the World Health Organization's (WHO) standards for yellow fever vaccine.
As of May 2025, the U.S. Food and Drug Administration (FDA) approved the YF-VAX vaccine (BL 103915, 103915/5220), and the U.S. Centers for Disease Control and Prevention (CDC), the U.S. Dept of Defense (DoD), and other health agencies have recommended YF-VAX since 2016. As of April 23, 2025, the YF-VAX vaccine is commercailly available at certified clinics and travel pharmacies in the U.S.
The FDA reported that 'two live, attenuated yellow fever vaccines, strains 17D-204 and 17DD, were derived in parallel in the 1930s. Historical data suggest that "17D vaccines" have identical safety and immunogenicity profiles. Therefore, vaccination with 17D strain vaccines is expected to elicit an immune response similar to wild-type infection. This response is presumed to result from the initial infection of cells in the dermis or other subcutaneous tissues near the injection site, with subsequent replication and limited spread of the virus leading to the processing and presentation of viral antigens to the immune system, as would occur during infection with wild-type yellow fever virus. Therefore, the humoral immune response to the viral structural proteins, as opposed to a cell-mediated response, is most important in the protective effect of 17D vaccines.
Sanofi Pasteur announced that effective April 5, 2021, YF-VAX® (NDC Code: 49281-915-01) became available again in the U.S. and is now available at authorized YF-VAX providers. According to the IHR (2005) third edition, the international vaccination certificate against yellow fever becomes valid ten days after vaccination, and its validity extends throughout the vaccinated person's lifetime.
Sanofi Pasteur, a Sanofi company, aims to ensure continued access to yellow fever vaccination for travelers to international destinations where the vaccine is required or recommended. Sanofi is dedicated to supporting people through their health challenges. On December 26, 2020, the FDA licensed the new Sanofi Pasteur YF-VAX production facility, and doses continue progressing through manufacturing. Efforts are underway to build an inventory and supply of YF-VAX, which will continue to be prioritized for the U.S. military.
Eliminate Yellow Fever Epidemics Strategy
Yellow fever (YF) virus is a single-stranded RNA virus belonging to the genus Flavivirus. It is transmitted to humans via the bite of an infected mosquito. The WHO published the Eliminate Yellow Fever Epidemics, a global disease prevention strategy. The ten-year EYE Strategy is a worldwide coalition of over 50 partners in 40 countries that has been accelerating efforts to prevent yellow fever outbreaks, protect at-risk populations, and save lives worldwide since 2017. According to EYE Strategy data, 226 million more people in Africa have been protected from yellow fever through a single-dose vaccine.
Yellow Fever Boosters
The U.S. CDC states that a yellow fever vaccine booster dose is not necessary. The Brazilian government said that individuals who received a fractional dose of the yellow fever vaccine in 2018 and will travel to São Paulo, Minas Gerais, Roraima, and Tocantins in 2025 should receive an additional dose in the standard presentation. As of April 2024, the findings from a study support the International Health Regulations, stating that a single-dose yellow fever vaccination provides lifelong protection for travelers.
YF-Vax Vaccine Price
Sanofi Pasteur and the U.S. CDC have confirmed the YF-VAX® vaccine is available in certified pharmacies and travel clinics. Sanofi's Patient Connection® offers various vaccine price savings. Sanofi has live support specialists at (800) 633-1610 to answer patients' questions. The CDC's Vaccines For Children program provides vaccines at no cost to qualifying children.
YF-VAX Vaccine Indication
Yellow fever is an acute viral hemorrhagic disease transmitted by infected mosquitoes. The "yellow" in the name refers to jaundice, a condition that affects some patients. The YF-VAX vaccine is indicated for active immunization to prevent yellow fever in individuals nine months of age and older at increased risk for yellow fever, to help prevent them from contracting it. However, vaccination with YF-VAX may not protect all individuals.
YF-VAX should not be given to individuals who have experienced a severe allergic reaction to eggs, egg products, or any vaccine component (gelatin). In addition, the following persons should not receive YF-VAX: infants younger than nine months of age due to an increased risk of brain inflammation, women breastfeeding infants younger than nine months, and individuals with a severely suppressed or compromised immune system. Therefore, the risk of disease versus the risk of a severe adverse event should be assessed before vaccine administration.
Geriatrics: YF-VAX® is indicated in persons 60 years of age and above. Pediatrics: YF-VAX® is indicated in persons nine months of age or older. Vaccination of infants under nine months of age IS CONTRAINDICATED because of the risk of encephalitis, and travel of such persons to rural areas in yellow fever endemic zones or countries experiencing an epidemic should be postponed or avoided whenever possible. Pregnant Women: Pregnant women should be considered for immunization only if travel to an area with a risk of yellow fever is unavoidable. It is also unknown whether the YF-VAX vaccine can cause fetal harm when administered to a pregnant woman or affect reproductive capacity. Therefore, the YF-VAX vaccine should only be given to a pregnant woman if needed. Additionally, the seroconversion rate to 17D vaccines is significantly reduced in pregnant women.
YF-VAX Vaccine Side Effects
YF-17D vaccines are considered among the safest and most efficacious vaccines available. Adverse events (AEs) following vaccination are usually mild. The most common side effects of YF-VAX include swelling and pain at the injection site, headache, generalized muscle aches or discomfort, and fever. Other side effects may occur. YF-VAX vaccine should not be given to an individual who has experienced a severe allergic reaction to eggs, egg products, or a vaccine component using gelatin. A severe allergic reaction (e.g., anaphylaxis) may occur following the use of the YF-VAX vaccine, even in individuals with no prior history of hypersensitivity to the vaccine components. Rarely has the yellow fever vaccine been associated with disease affecting multiple organs, including brain inflammation.
YF-VAX Vaccine Breastfeeding
Since 2010, there have been health concerns about lactating mothers breastfeeding infants following yellow fever vaccinations. As of 2023, two serious adverse events have been reported in breastfed infants whose mothers were vaccinated with the Yellow Fever vaccine. Until more information is available, the U.S. CDC says the Yellow Fever vaccine should be avoided in breastfeeding women.
YF-VAX Vaccine Drug Interactions
Data are limited regarding the drug interaction of the YF-VAX vaccine with other vaccines, such as the Measles (Schwartz strain) vaccine, diphtheria, tetanus toxoid, and pertussis vaccine adsorbed. Hepatitis A and B vaccines, meningococcal vaccine (Menomune A/C/Y/W-1), typhoid vaccine (Typhim Vi), and the yellow fever vaccine have been administered at separate injection sites. No data exist on possible interference between yellow fever and rabies or Japanese encephalitis vaccines.
YF-VAX Vaccine Immunocompromised
A meta-analysis published in August 2022 concluded that there are theoretical contraindications to using the YF vaccine in immunocompromised individuals; however, the increased risk of adverse events has not been confirmed.
YF-VAX Vaccine Breakthrough Infections
As documented in the literature, breakthrough infections with the yellow fever vaccine are rare. In December 2024, a study found that the pooled percentage of verified yellow fever breakthrough infections among probable and confirmed cases was 3% (95% CI 1-19%). No confirmed breakthrough infections that occurred 10 years or more after vaccination against yellow fever have been identified.
YF-VAX Vaccine Dosage
YF-VAX is administered as a single subcutaneous injection of 0.5 mL of reconstituted vaccine. Do not administer YF-VAX by intravascular, intramuscular, or intradermal routes. A single dose protects most people for ten years. Sanofi Pasteur's complete YF-VAX Vaccine Prescribing Information is available. The vial stoppers for YF-VAX and diluent are not made with natural rubber latex.
Yellow Fever International Certificate of Vaccination or Prophylaxis
Certain countries may have requirements to protect individual travelers and countries from the risk of importing or spreading the yellow fever virus. These requirements apply to the country you will be visiting; in that case, you may need the 'yellow fever card,' the International Certificate of Vaccination (ICVP), or Prophylaxis as proof of vaccination. The ICVP becomes effective ten days after vaccination is administered.
YF-VAX Vaccine News
April 15, 2025 - The U.S. CDC issued a Level 2 Travel Health Advisory for the yellow fever outbreak in South America.
December 30, 2023 - Study: Phylogenetic analysis reveals a new introduction of the Yellow Fever virus in São Paulo State, Brazil, 2023.
October 28, 2023 - The Africa CDC confirmed active yellow fever outbreaks in seven countries.
March 21, 2023 - Study: Enhanced safety surveillance of yellow fever vaccine provided under the expanded access investigational new drug program in the USA.
April 25, 2023 - The PAHO confirmed additional yellow fever cases and related fatalities.
January 15, 2023 - The WHO Africa reported one yellow fever-related fatality in an unvaccinated young woman in Guinea.
January 3, 2023 - The WHO African Region reassessed the risk at the regional level as moderate in December 2022, after it was previously reported as high in November 2021 and June 2022. The global risk remains low, as no cases related to this current African outbreak have been reported outside the African region.
September 2, 2022 - According to the WHO EYE strategy, twenty-seven African countries are at high risk for yellow fever based on the timing and intensity of yellow fever virus transmission, transmission potential, and urban risk assessment. The chance of a global outbreak is assessed to be low, as no exported cases of yellow fever linked to these 12 countries with probable or confirmed cases have been reported since January 2021.
July 31, 2022 - According to the U.S. CDC, approximately thirty countries are considered 'endemic' for the mosquito-borne yellow fever virus.
March 8, 2022: BMC reported on the 'Changing epidemiology of yellow fever virus in Oyo State, Nigeria.'
April 5, 2021 - The U.S. CDC confirmed that Sanofi Pasteur announced that YF-VAX is again available for purchase in the USA. Providers with a current Yellow Fever Vaccination Stamp issued by their state or territorial health department may order YF-VAX from the manufacturer.
December 23, 2020—Sanofi Pasteur confirmed that the U.S. Expanded Access Investigational Drug Application Program (EAP) for STAMARIL® would continue into 2021. Therefore, when YF-VAX returns, a brief transition period will occur before discontinuing the STAMARIL EAP.
June 25, 2020 - The U.S. FDA has licensed Sanofi Pasteur's new U.S. YF-VAX vaccine production facility, and doses continue progressing through manufacturing.
December 23, 2019 - Sanofi has collaborated with the U.S. Food and Drug Administration (FDA) to provide the STAMARIL vaccine through an Expanded Access Program (EAP) during the YF-VAX vaccine shortage.
August 6, 2019 - The U.S. FDA approved an Expanded Approval Letter for the YF-VAX yellow fever vaccine.
May 2, 2019 – The Food & Drug Administration (FDA) has licensed a new state-of-the-art yellow fever vaccine production facility in the USA. According to a statement from Sanofi Pasteur, the production transition of YF-VAX is ongoing.
January 25, 2018 - Brazil launched a mass immunization campaign to deliver fractional doses of yellow fever vaccine to residents of 69 municipalities in Rio de Janeiro and São Paulo.
June 15, 2016 - FDA Approval Letter - To revise the YF-VAX package insert to align Booster Dosing language with recent changes to International Health Regulations and WHO/ACIP recommendations and modify the text throughout the document to clarify and update the presented information.
YF-VAX Yellow Fever Vaccine Clinical Trials
YF-VAX continues to be studied in various clinical trials.
