Yellow fever vaccination: rules and certificate

Yellow fever is an acute viral hemorrhagic infection transmitted by mosquitoes of the genera Aedes, Haemagogus, and Sabethes. The disease can rapidly progress to a severe form with liver damage and a high risk of death. There is no specific treatment that can reliably stop the virus from replicating, so the key preventative measures are vaccination and protection from mosquito bites. [1]

The yellow fever vaccine is a live-attenuated vaccine of the 17D lineage. It has been used for over 60 years, produces lasting immunity in the vast majority of those vaccinated, and is considered safe when the indications and contraindications are followed. A single dose is typically sufficient, providing long-term, and according to international organizations, lifelong, protection. [2]

The International Sanitary Regulations (ISR) stipulate that the International Certificate of Vaccination is valid for the entire life of the vaccinated person, beginning 10 days after the initial dose. This rule is legally valid for all countries that are signatories to the ISR. [3]

Epidemiology and risk for travelers

Transmission of the infection is endemic in several countries in tropical Africa and Latin America. Annual reports confirm outbreaks and fatalities, maintaining a high priority for prevention for residents and travelers. In 2025, the European Centre for Disease Control reported confirmed cases in South America, emphasizing the need to consider travel routes and transit. [4]

Outbreaks are driven by a combination of factors: virus circulation among wild primates, the presence of vectors in forest and peridomestic habitats, and incomplete vaccination coverage. The World Health Organization emphasizes the importance of the disease to global health security due to the potential for international spread. [5]

For Europe, the main concern is imported cases and potential transmission in the presence of viable vectors. Risk guidelines for Aedes mosquito-borne infections recommend considering seasonal factors, exposure levels, and local risk scenarios. [6]

Who is eligible for vaccination and when is it mandatory?

Vaccination is recommended for individuals living, working, or planning to travel to endemic areas, as well as laboratory workers potentially exposed to the virus. For travelers, the decision is based on a combination of factors: region, season, length of stay, local conditions, and ability to avoid mosquito bites. [7]

Some countries require a valid International Certificate of Vaccination upon entry from countries where there is a risk of virus transmission, including transit situations with long layovers. If there are medical contraindications, an official medical exemption may be included in the same certificate. It is important for travelers to check both the health recommendations and the formal requirements of the specific country. [8]

The certificate becomes valid 10 days after the initial vaccination and remains valid for life. Refusal of entry on the grounds of "expiry of 10 years" is contrary to the International Health Regulations and should not be applied. [9]

Table 1. When vaccination is recommended and when documentation is required

Situation	Medical recommendation	Demand at the border
A trip to an endemic region with active outdoor activities	Vaccination is recommended	A certificate is often required when entering from risk countries.
A short visit to an urban area with no plans to travel to rural areas	Discussed individually depending on the level of exposure	It may not be required, but rules vary by country.
Long-term work in field conditions	Highly recommended	Often required
Medical exemption	They don't vaccinate	A medical exemption may be included in the certificate.

Sources: CDC travel advisories by country, International Health Regulations.[10]

What vaccines are used and what are their compositions?

Most countries use live attenuated vaccines based on the 17D strain. For example, Stamaril contains a live attenuated virus and excipients according to the approved instructions. These drugs are administered once in a standard volume, ensuring the development of a protective immune response. [11]

Long-term experience confirms their sustained immunogenicity and wide geographic distribution. The World Health Organization and the Pan American Health Organization consider these vaccines a key tool for the prevention and control of outbreaks. [12]

Table 2. Examples of yellow fever vaccines

Name	Type	Main strain	Peculiarities
Stamaril	Live attenuated	17D	One dose for primary immunization
Other registered variants of 17D	Live attenuated	17D	National registrations, single dose regimen

Sources: regulatory materials and summary pages. [13]

Vaccination schedule, validity period and boosters

The basic regimen for children 9 months and older and for adults is one dose. The certificate becomes valid 10 days after vaccination. Most healthy people do not require a booster dose. [14]

The International Sanitary Regulations (ISR) establish lifelong validity of the certificate after the initial dose, with no mandatory "re-vaccinations" to maintain the document. This was legally established on July 11, 2016, and is in effect in all participating countries. [15]

Some national guidelines allow booster doses in specific situations: in people with a continuing high risk of exposure many years after the initial dose, in those vaccinated during pregnancy, in those who have undergone a hematopoietic cell transplant, and in certain immunocompromised patients. The decision is made on an individual basis, assessing the benefits and risks. [16]

Table 3. Timing and indications for revaccination

Category	Do I need a default booster?	When to consider a booster
Healthy adults and children over 9 months	Not required	Very long-term exposure in high-risk areas as determined by a specialist
Vaccinated during pregnancy	Not required by most	Consider a booster seat for future travel to high-risk areas.
Those who have undergone a hematopoietic cell transplant	Not required automatically	Consider after restoration of immunity and according to indications
Certain forms of immunodeficiency	Not required by most	Individual assessment based on risk level and recommendations of the host country

Sources: ACIP and travel guides.[17]

Efficiency

Live attenuated vaccines of the 17D lineage induce neutralizing antibodies in the vast majority of those vaccinated. International organizations consider immunity to be long-lasting, even lifelong, after a single dose in immunocompetent individuals. This is confirmed by many years of successful use in mass campaigns. [18]

From a practical standpoint, this means that with timely vaccination before travel, in the absence of immune deficiencies, and adherence to mosquito protection measures, the risk of illness is significantly reduced. It is important to note, however, that no vaccine provides an absolute guarantee, so non-specific preventative measures remain important. [19]

Safety and side effects

Common reactions are usually mild and short-lived: soreness and redness at the injection site, weakness, headache, and muscle pain. These symptoms occur more frequently in the first few days and resolve on their own. [20]

Rare but important complications include vaccine-associated neurotropic disease and vaccine-associated viscerotropic disease. According to the US Centers for Disease Control and Prevention, the estimated rates are approximately 0.8 cases per 100,000 doses for the neurotropic form and approximately 0.3 cases per 100,000 doses for the viscerotropic form, with the risk being higher in people over 60 years of age. The viscerotropic form has the highest mortality rate and has been described almost exclusively after the first dose. [21]

The World Health Organization's Global Advisory Committee on Vaccine Safety confirms the rarity of these outcomes and emphasizes that cases have been reported primarily after primary vaccination. This is taken into account when assessing the benefits and risks in older age groups and in the presence of risk factors. [22]

Table 4. Common and rare adverse events

Category	Examples	Estimated frequency
Local reactions	Pain, redness, swelling	Often, briefly
Systemic lungs	Weakness, headache, myalgia	Often, briefly
Neurotropic disease	Encephalitis-like manifestations	About 0.8 per 100,000 doses, higher in those 60 plus
Viscerotropic disease	Multiple organ dysfunction	About 0.3 per 100,000 doses, higher in those 60 plus

Sources: clinical guidelines and safety summaries. [23]

Contraindications and precautions

Absolute contraindications: age under 6 months, severe allergic reaction to vaccine components, severe immunodeficiency, malignant neoplasms on active immunosuppressive therapy, history of thymus diseases with impaired immune cell function, such as thymoma or myasthenia gravis. In these conditions, the risk of serious complications is higher; the vaccine is not used. [24]

Vaccination of children aged 6 to 9 months, pregnant and breastfeeding women, and people over 60 years of age is approached with caution. The decision in these groups is made by a physician after assessing the individual risk of infection and potential benefit, as well as taking into account alternative travel routes and the possibility of a medical exemption. [25]

Table 5. Who should not or should not be vaccinated

Group	Position
Infants up to 6 months	Contraindicated
True anaphylaxis to components	Contraindicated
Severe immunosuppression	Contraindicated
Thymus diseases with impaired immune function	Contraindicated
Age 6-9 months, pregnancy, lactation, age 60 plus	Individual risk-benefit assessment

Sources: international guidelines and instructions. [26]

Compatibility with other vaccinations and medications

Co-administration with most live vaccines is acceptable. However, research data suggests that co-administration with the combined measles, mumps, and rubella vaccine may reduce the immune response to individual antigens, so if time permits, it is preferable to separate administrations by 28-30 days. If time is limited, co-administration is permitted to ensure protection before travel. [27]

There are no contraindications for combining antimalarial drugs with the vaccine described in travel preparation guidelines. Anti-mosquito control measures and malaria chemoprophylaxis are selected regardless of yellow fever vaccination status. [28]

Table 6. Intervals with other live vaccines

Combination	Recommended interval for time diversity	Admissibility of simultaneous administration
With the measles, mumps, and rubella vaccine	Preferably 28-30 days	Allowed when time is short
With other live parenteral vaccines	Usually 28 days	Allowed for clinical necessity
With inactivated vaccines	No special intervals are required	Allowed

Sources: Travel guides and expert immunization guidance.[29]

Documents and rules for crossing borders

An International Certificate of Vaccination or Prophylaxis is issued by an authorized center. The initial dose makes the certificate valid from the 10th day, and the document remains valid for life. If there are contraindications, a medical exemption is included in the certificate, which countries are required to honor. Travelers should check both the medical recommendations for the risk and the formal requirements of the specific country and possible transit points. [30]

Post-vaccination monitoring and when to contact a doctor

A doctor should be consulted if a high fever, severe systemic symptoms, severe headache, neurological signs, or signs of liver dysfunction develop within the first weeks after vaccination. Elderly patients and those in high-risk groups should be monitored particularly closely. Early notification of medical services is important to assess the likelihood of rare complications and provide timely assistance. [31]

Practical steps for the traveler

1. Check the endemicity of the regions along the route, including transit times exceeding 12 hours, and verify certification requirements. [32]
2. Schedule your vaccination at least 10 days before departure for your certificate to be valid. [33]
3. In groups of questionable tolerability or older age, discuss the individual benefit-risk ratio. [34]
4. Regardless of vaccination, use repellents, long-sleeved clothing and nets, and choose housing with screens on the windows. [35]