How Old Do You Have to Be To Receive Yellow Fever Vaccine?

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Patient Presentation
A 2-year-old female came to clinic for her health supervision visit. The parents had no concerns but were going to be traveling to the Republic of the Congo for 2 months.

The pertinent physical exam showed growth parameters in the 50-75% with normal vital signs. Her examination was normal.

The diagnosis of a healthy female was made who would be traveling to an area endemic for several infectious diseases. The patient was current with her routine vaccines including Hepatitis A, Influenza and COVID. The pediatrician consulted the Centers for Disease Control website for vaccine recommendations for the Congo which indicated the need for malaria prophylaxis as well as Yellow Fever and Typhoid vaccine. The pediatrician provided travel guidance including that for water-borne, mosquito-borne and animal exposures to the family. She also provided a prescription for malaria prophylaxis and referred the family to the regional Yellow Fever clinic where she also knew the patient could received Typhoid vaccine as well.

Discussion
In the United States, Yellow Fever (YF) is rare and usually due to traveler’s coming to the US from Africa (34 countries) or South America (13 countries, see maps here) This wasn’t always true. There were numerous outbreaks in the past few centuries. However, after the Spanish-American War, a YF commission was sent to Cuba that proved YF was mosquito-borne and 1 year later major improvement was seen due to a multi-pronged mosquito control program.

“In May 1900, the U.S. Army,…formed the U.S. Army Yellow Fever Commission to gather data in Cuba that might inspire improvements in the public health campaign. A little-known medical army medical researcher, Major Walter Reed, was appointed to lead the group….
[T]he public health campaign of 1901 was historic. The occupation government instituted an unprecedented mosquito control program in Havana. Brigades of Cuban workers fumigated houses, eliminated sources of standing water, and quarantined infected yellow fever patients in rooms protected by mosquito nets. The results were dramatic. In less than a year, yellow fever had been virtually eradicated in Havana, providing the ultimate demonstration that [the] mosquito theory was correct.”

One of the US’s national military medical centers in Bethesda Maryland is named for Walter Reed.

YF is endemic in parts of all of 47 countries. In 2013, it caused 84-170,000 severe cases and 29-60,000 deaths. It is a mosquito-borne Flavivirus. Aedes and Haemagogus mosquitoes which spread YF are day-biting and live in homes (both urban and non-urban) and forest or jungles. YF is a mimic of other tropical diseases including malaria, hemorrhagic fevers, other Flavivirus diseases such as dengue, plus other causes of hepatitis. The incubation period is 3-6 days, symptomatic period of 3-4 days with fever, headache, muscle pain, nausea, emesis, or appetite loss. In most cases, symptoms disappear after 3 to 4 days but there can be a second more severe phase that occurs about 24 hours after the resolution. This more severe phase can cause multi-organ system failure particularly hepatotoxicity with jaundice, abdominal pain, and coagulopathy/bleeding. Death occurs in about 50% of those in this severe phase. Diagnosis is by polymerase chain reaction testing.

Learning Point
YF prevention and prompt treatment of outbreaks are key. Mosquito control and eradication through public health measures is important. Individuals in YF endemic areas should monitor and mitigate their standing water sources and consistently use mosquito netting properly although this is less effective due to these being day-biting mosquitos.

YF vaccine is highly effective (80-90% protection at 10 days and 99% at 30 days) and provides life-long protection with one dose. In some cases, some specific individuals may need a booster. The vaccine is a live-attenuated vaccine routinely used in endemic areas. Children > 9 months are recommended to receive the vaccine if appropriate and there are few other contraindications (e.g. pregnancy, immunodeficiency or egg allergy). Potentially a child could receive it from age 6 months such as in an outbreak situation. If a child is traveling to an endemic area and has a specific contraindication they should receive a physician-waiver before traveling indicating the contraindication. The vaccine can cause rare side-effects. YF-associated viscerotropic disease (YEL-AVD) presents similarly to YF severe disease and can cause multi-organ system failure and death. YF-associated neurotropic disease (YF-AND) is rarely fatal but can cause meningoencephalitis or encephalitis.

A 2020 literature review of routine vaccine safety in Africa reviewed 15 years of information and found few adverse events (24 serious and 23 minor) for 9 routine vaccines including VF. There were suspected YF-AND and YF-AVD cases. They cite that additional studies are needed for YF and another additional study that concluded, …”yellow fever vaccination should be limited to persons traveling to areas where the risk of yellow fever is expected to exceed the risk of serious adverse events after vaccination, or if not medically contraindicated, where national regulations require proof of vaccination to prevention introduction of yellow fever.”

Questions for Further Discussion
1. What are the general recommendations for foreign travelers regarding water-borne and mosquito-borne diseases?
2. What do you consider when choosing malaria prophylaxis medications?
3. Where is your closest provider for Yellow Fever vaccine?
4. List other hemorrhagic fevers?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Hemorrhagic Fevers

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

PAHO/WHO | Yellow Fever. Pan American Health Organization / World Health Organization. Published April 24, 2014. Accessed August 7, 2023. https://www3.paho.org/hq/index.php?option=com_content&view=article&id=9476:yellow-fever&Itemid=0&lang=en#gsc.tab=0

Yamoah P, Bangalee V, Oosthuizen F. A review of the safety of vaccines used in routine immunization in Africa. Afr Health Sci. 2020;20(1):227-237. doi:10.4314/ahs.v20i1.28

Vijayan V. Vaccines for International Pediatric Travelers. Pediatr Clin North Am. 2022;69(1):171-184. doi:10.1016/j.pcl.2021.08.009

Yellow fever fact sheet. World Health Organizaiton. Accessed August 7, 2023. https://www.who.int/news-room/fact-sheets/detail/yellow-fever

Yellow fever. World Health Organization. Accessed August 7, 2023. https://www.who.int/health-topics/yellow-fever

Walter Reed and the Scourge of Yellow Fever. Accessed August 8, 2023. https://news.virginia.edu/content/walter-reed-and-scourge-yellow-fever

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

Published