What Is YF-Vax? Uses, Dosage, and What You Need to Know in 2026

YF-Vax is a vaccine used to prevent yellow fever — a potentially fatal viral illness spread by infected mosquitoes in parts of Africa and South America. If you're planning international travel to a region where yellow fever is present (or required for entry), YF-Vax is the vaccine your travel medicine provider will give you.

Here's a complete overview of YF-Vax — what it is, who needs it, how it's given, and key facts for 2026.

What Is YF-Vax?

YF-Vax (Yellow Fever Vaccine) is a live-attenuated viral vaccine manufactured by Sanofi Pasteur, Inc., based in Swiftwater, Pennsylvania. It is the

only yellow fever vaccine licensed by the FDA for use in the United States. The vaccine is made using the 17D-204 strain of the yellow fever virus, grown in avian leukosis-free chicken embryos. It contains sorbitol and gelatin as stabilizers, is freeze-dried (lyophilized), and contains no preservatives.

Before reconstitution, YF-Vax is a pinkish powder. After reconstitution with the provided Sodium Chloride Injection diluent, it becomes a slight pink-brown suspension. It must be administered within 60 minutes of reconstitution.

Who Is YF-Vax For?

YF-Vax is recommended for:

People 9 months of age and older traveling to or living in areas of Africa and South America with known risk of yellow fever virus transmission

Travelers going to countries that require proof of yellow fever vaccination for entry (ICVP requirement)

Laboratory workers who handle live yellow fever virus or concentrated vaccine virus strains

YF-Vax is

not recommended for routine use in people not traveling to yellow fever risk areas, and it is contraindicated in infants under 6 months, severely immunocompromised individuals, and people with thymus disorders.

YF-Vax Dosage and How It's Given

A single subcutaneous injection of 0.5 mL is the standard dose for all eligible patients aged 9 months and older. The vaccine must be given via the subcutaneous route — not intravenous, intramuscular, or intradermal.

YF-Vax is available in single-dose vials (with individual diluent) and multi-dose 5-dose vials. The 5-dose vials must be used in batch vaccination settings, as reconstituted vaccine expires within 60 minutes.

How Long Does YF-Vax Protect You?

A single dose of YF-Vax provides long-lasting protection for most healthy individuals. A 2024 systematic review in The Lancet Global Health concluded that a single dose of yellow fever vaccination provides lifelong protection for travelers. Under current WHO International Health Regulations (IHR), the ICVP is valid for the lifetime of the vaccinee — no booster is required for most people.

However, certain groups may benefit from a booster dose:

Travelers who received the vaccine more than 10 years ago and are entering high-risk areas during active outbreaks

HIV-positive individuals who received the vaccine when their HIV was active

Recipients of hematopoietic stem cell transplants after previous vaccination

The International Certificate of Vaccination or Prophylaxis (ICVP)

After receiving YF-Vax, you will be issued an ICVP — commonly called the "yellow card" or "yellow vaccination certificate." This is an internationally recognized document that proves you have been vaccinated against yellow fever. Under the IHR, the ICVP becomes valid 10 days after vaccination and, as of 2016, is valid for life.

Some countries require the ICVP as a condition of entry, particularly for travelers arriving from yellow-fever-endemic regions. Always check current country-specific entry requirements before travel.

Where to Get YF-Vax in 2026

YF-Vax can only be administered at authorized Yellow Fever Vaccination Centers — sites that hold a valid Yellow Fever Vaccination Stamp from their state or territorial health department. The national shortage that ran from 2015–2021 has been resolved; YF-Vax is commercially available at certified travel clinics as of early 2026.

To find a clinic near you that currently has YF-Vax in stock, use medfinder — we call authorized clinics on your behalf and text you back with results.

Learn more: how YF-Vax works | YF-Vax side effects.