Travel vaccines are recommendations by government health agencies for people who want to travel to a country where different infectious micro-organisms, ie. viruses, bacterias are more prevalent or endemic.

On this page I will provide information for some commonly recommended vaccines. This is for educational purposes only, I am merely collating publicly available information into one place for your convenience. Please discuss your concerns with your trusted physician so you can make an informed medical decision.

What travel vaccines does the CDC recommend?

It can vary by country. The CDC’s website contains their specific vaccine recommendations for every country. I won’t be able to provide all that info here, but I can highlight some of the more commonly recommended vaccines. For example, before traveling to most countries, the CDC recommends the following routine vaccines:

• Varicella (chickenpox)
• DTP
• Flu
• MMR
• Polio
• Shingles
• COVID-19

For a country like Nigeria, the CDC also encourages and/or recommends:

• Chikungunya (65+ and people staying for 6+ months)
• Cholera (for children and adults traveling in areas of active transmission)
• Hepatitis A
• Hepatitis B
• Meningitis (Meningococcal) (For travelers 2 months + who are traveling to the “meningitis belt”
• Rabies (Consult your healthcare provider –  per the CDC)
• Typhoid (Recommended for most travelers)
• Yellow Fever (Recommended for all travelers >9 months of age)

That may look like a lot of vaccines. But before you cancel your flight, let me give you some more hopefully useful information.

*My plan is to add many travel vaccines, but for now I’ve only completed Yellow Fever, due to request.

Yellow Fever

Yellow fever is caused by a virus in the Flavivirus genus and is transmitted from an infected mosquito bite. These infected mosquitos can be found in tropical and subtropical areas in South America and Africa. It is believed that yellow fever virus originated in Africa, and was brought to North and South America by way of the Spanish conquerers and during the slave trade.

Symptoms

Yellow fever can present with varying clinical symptoms that range from asymptomatic to a self-limited, mild febrile illness, to a severe hemorrhage and liver disease, hence the name, yellow fever. Incubation is 3-6 days.

After incubation, an infected person may experience:

• fever
• chills
• severe headache
• back pain
• general body aches
• nausea
• vomiting
• fatigue (feeling tired)
• weakness

Severe cases

• high fever
• yellow skin or eyes (jaundice)
• bleeding, shock, and organ failure

Risk factors for severe disease

The CDC states around 12% of infected persons progress to the more severe hemorrhagic symptoms, and of those 30%-60% are fatal. Risk factors for severe disease include:

• Age: the elderly and infants less than 9 months are at higher risk
• HIV infection or compromised immune system
• Malnutrition
• Immunosuppressive medication
• Pre-existing liver, kidney, cardiovascular disease
• High viral dose, ie. a lot of bites
• Delayed medical care

How many people are affected by yellow fever?

This website has reported cases by country, by year. It’s very common for an infectious disease to be underreported, but this gives you an idea of how many cases of a disease are reported, which helps quantify your risk.

For example, in Nigeria in 2022, there were 14 cases of yellow fever reported, and in 2021, there were 54 cases, in 2020 there were 216 cases.

According to the study “Changing epidemiology of yellow fever virus in Oyo State, Nigeria” in 2020 there were 51 cases of suspected yellow fever for an incidence rate of 5.6 per 100,000 population. 

The paper looked at yellow fever cases over a several year period, and found:

“In total, 93 of 240 (39%) suspected yellow fever cases reported during the given period were observed to have received yellow fever vaccine. Furthermore, 61 of the 240 (25%) were unvaccinated, and 86 (36%) had unknown vaccination status. At least, half of the suspected yellow fever cases reported in the year 2013 to 2016 had received yellow fever vaccine while less than 50% of suspected cases in 2017 to 2020 had been vaccinated against Yellow Fever with the years 2017 and 2020 recording only about a quarter 26% and 22% respectively, of all suspected cases who had received Yellow Fever vaccine.”

There is no specific medications according to the CDC for the treatment of Yellow fever virus infections. Fluids, rest, etc are recommended. Avoidance of aspirin and other nonsteroidal anti-inflammatory drugs are encouraged as they can increase risk for bleeding.

Avoiding mosquito bites is one way to prevent Yellow fever.

• Wearing long sleeve clothing
• Sleep with mosquito nets
• Keep windows closed
• Use mosquito repellants, sprays, lotions, ointments, bracelets, candles
• Avoid being outside during highest mosquito activity (mid-morning, late afternoon to twilight)

The Yellow fever vaccine is another option to prevent yellow fever infection.

 Yellow Fever Vaccine (YF-VAX) Insert 

• Manufacturer: Sanofi Pasteur, Inc
• Route: Subcutaneous
• Age: For active immunization of persons 9 months of age and older

Description

YF-VAX®, Yellow Fever Vaccine, for subcutaneous use, is prepared by culturing the 17D-204 strain of yellow fever virus in living avian leukosis virus-free (ALV-free) chicken embryos. The vaccine contains sorbitol and gelatin as a stabilizer, is lyophilized, and is hermetically sealed under nitrogen. No preservative is added. Each vial of vaccine is supplied with a separate vial of sterile diluent, which contains Sodium Chloride Injection USP – without a preservative. YF-VAX is formulated to contain not less than 4.74 log10 plaque forming units (PFU) per 0.5 mL dose throughout the life of the product. Before reconstitution, YF-VAX is a pinkish color. After reconstitution, YF-VAX is a slight pink-brown suspension. The vial stoppers for YF-VAX and diluent are not made with natural rubber latex.

YF-VAX is a live attenuated viral vaccine made from a weakened version of the virus, strain 17D-204.

When not administered concomitantly, wait at least 4 weeks between administration of YFVAX and other live vaccines.

Has the Yellow fever vaccine undergone a placebo controlled trial?

According to the vaccine insert:

“No placebo-controlled trial has assessed the safety of YF-VAX.”

Contraindications

Hypersensitivity

YF-VAX is contraindicated in anyone with a history of acute hypersensitivity reaction to any component of the vaccine. (See DESCRIPTION section.) Because the yellow fever virus used in the production of this vaccine is propagated in chicken embryos, do not administer YF-VAX to anyone with a history of acute hypersensitivity to eggs or egg products due to a risk of anaphylaxis. Less severe or localized manifestations of allergy to eggs or to feathers are not contraindications to vaccine administration and do not usually warrant vaccine skin testing.

Infants less than 9 months of age

Vaccination with YF-VAX is contraindicated in infants less than 9 months of age due to an increased risk of encephalitis. Vaccination with YF-VAX is also contraindicated in lactating women who are providing breastmilk to infants less than 9 months of age due to the potential for transmission of vaccine virus in breastmilk.

Immunosuppressed individuals

Vaccination with YF-VAX, a live virus vaccine, is contraindicated in individuals with severe immunosuppression, including for example, those with acquired immunodeficiency syndrome, 3 leukemia, lymphoma, thymic disease, generalized malignancy, and patients who are undergoing drug therapy (e.g., systemic corticosteroids, alkylating drugs, antimetabolites or other immunomodulatory drugs) or radiation therapy. Thymic disorders associated with abnormal immune cell function (e.g., myasthenia gravis, thymoma) may be an independent risk factor for the development of yellow fever vaccine-associated viscerotropic disease.

Postmarketing experience

• Injection-site blisters
• Immediate hypersensitivity reactions or anaphylaxis
• Yellow Fever Vaccine-Associated Neurotropic Disease
• Yellow Fever Vaccine-Associated Viscerotropic Disease
• Guillain-Barré syndrome (GBS)
• acute disseminated encephalomyelitis (ADEM)
• bulbar palsy
• thrombocytopenia
• lymphopenia
• acute renal failure

Vaccine efficacy

The World Health Organization states:

The vaccine provides effective immunity within 10 days for 80–100% of people vaccinated, and within 30 days for more than 99% of people vaccinated.

A 2022 paper “Yellow Fever: Origin, Epidemiology, Preventive Strategies and Future Prospects” states:

“Individuals vaccinated against YF show high levels of protection with a seroconversion rate greater than 95% in both adults and children. However, it has been seen that children less than two years of age may show a lower level of seroconversion after a single dose of vaccine.“

From the insert:

“In 2001, YF-VAX was used as a control in a double-blind, randomized comparison trial with another 17D-204 vaccine, conducted at nine centers in the US. YF-VAX was administered to 725 adults ≥18 years old with a mean age of 38 years. Three hundred twelve of these subjects who received YF-VAX were evaluated serologically, and 99.3% of them seroconverted with a mean LNI of 2.21.”

However, this paper “Changing epidemiology of yellow fever virus in Oyo State, Nigeria” documented the vaccine status of reported infections and found that:

In total, 93 of 240 (39%) suspected yellow fever cases reported during the given period were observed to have received yellow fever vaccine. Furthermore, 61 of the 240 (25%) were unvaccinated, and 86 (36%) had unknown vaccination status. At least, half of the suspected yellow fever cases reported in the year 2013 to 2016 had received yellow fever vaccine while less than 50% of suspected cases in 2017 to 2020 had been vaccinated against Yellow Fever with the years 2017 and 2020 recording only about a quarter 26% and 22% respectively, of all suspected cases who had received Yellow Fever vaccine. 

A 2019 paper titled “Long-term immunity against yellow fever in children vaccinated during infancy: a longitudinal cohort study“ found:

“We included 587 Malian and 436 Ghanaian children vaccinated between June 5, 2009, and Dec 26, 2012. In the Malian group, 296 (50·4%, 95% CI 46·4–54·5) were seropositive (antibody concentration ≥0·5 IU/mL) 4·5 years after vaccination. Among the Ghanaian children, 121 (27·8%, 23·5–32·0) were seropositive after 2·3 years. These results show a large decrease from the proportions of seropositive infants 28 days after vaccination, 96·7% in Mali and 72·7% in Ghana, reported by a previous study of both study populations. The number of seropositive children increased to 188 (43·1%, 95% CI 38·5–47·8) in the Ghanaian group 6·0 years after vaccination, but this result might be confounded by unrecorded revaccination or natural infection with wild yellow fever virus during a 2011–12 outbreak in northern Ghana.”

It concludes:

“Rapid waning of immunity during the early years after vaccination of 9-month-old infants argues for a revision of the single-dose recommendation for this target population in endemic countries. The short duration of immunity in many vaccinees suggests that booster vaccination is necessary to meet the 80% population immunity threshold for prevention of yellow fever outbreaks.”

Another paper, “Questions regarding the safety and duration of immunity following live yellow fever vaccination” published in 2016 reports:

There were 831 cases of yellow fever identified between 1973–2008 with a case fatality rate of 51%. Vaccination status was unavailable for 372/831 (45%) of patients but the remaining 459 cases had received prior YFV vaccination and yet still contracted yellow fever. Since all of the cases of yellow fever were virologically confirmed, we believe that this is likely to be a more accurate representation of vaccine failures than the previous estimate of only 23 worldwide vaccine failures occurring between 1944–2013.

That paper is questioning the WHO’s assertion that the Yellow Fever vaccine provides lifelong immunity, pointing out instances and examples of vaccine waning with the motive to continuously recommend boosters. But it also provides us with some more relevant vaccine efficacy information, as it shows that 55% of yellow fever reported illnesses were in fact vaccinated.

It’s interesting on the one hand, the reports that claim 95% vaccine success are using blood work and seroconversion, whereas boots on the ground studies collecting reports of confirmed infection and documenting their vaccine status tells a slightly different story.

A 2024 randomized controlled clinical trial (sponsored by the US CDC) recruited Ugandan children aged 9-23 months presenting for routine well-child services to either receive a one-fifth and one-half doses of Bio-Manguinhos 17DD YF vaccine with full dose in children.

Among 1053 enrolled children, 672 (64%) were reported to have a non-serious AEFI (NSAE) (non-serious adverse event following immunization) and 17 (2%) were reported to have a SAE (serious adverse event). 

“The most common AEFI were diarrhoea, fever, and rash, each reported by 355 (34%), 338 (33%), and 188 (18%) participants, respectively. Among 17 participants with SAE, eight were reported to have had seizures and five were hospitalised for seizures or other causes (respiratory symptoms, gastrointestinal illness, malaria). Four SAEs (deaths) occurred >28 days after vaccination. There were no reported cases of pre-specified or vaccine-related SAEs. We observed no significant difference in frequency or severity of adverse events among the study groups.

Although we identified a high number of both serious and non-serious AEFI, none were determined to be causally related to YF vaccination.“

The 2005 study “Yellow fever vaccine: An updated assessment of advanced age as a risk factor for serious adverse events” writes: 

“Previously, YEL was believed to be one of the safest vaccines [1]. Since 1996, this belief has changed, when in the U.S., the first four cases of YEL-associated viscerotropic disease (YEL-AVD) and another four cases of YEL-associated neurotropic disease (YEL-AND) were reported.

Advanced age (65 years and older) was previously identified as a risk factor for systemic adverse events temporally associated with YEL [13], [14]. There is some evidence that YEL-AVD and YEL-AND also appear more frequently in persons of advanced age.”